内容

Contents

不同种族群体之间的融合是人类历史上反复出现的过程。这幅地图为本书讨论的三十次重大种族融合事件提供了关键线索。（地图上的位置并非精确位置。）

The mixture of highly differentiated populations is a recurrent process in our history. This map provides a key to thirty great mixture events discussed in this book. (Locations are not meant to be precise.)

第二章

CHAPTER 2

2a距今54000至49000年前

2a 54,000–49,000 years ago

所有非非洲裔人士

All non-Africans

尼安德特人 + 现代人类

Neanderthals + modern humans

第三章

CHAPTER 3

3a >70,000西伯利亚丹尼索瓦人

3a >70,000 ya Siberian Denisovans

超古血统 +

Superarchaic lineage +

尼安德特人相关谱系

Neanderthal-related lineage

3b 49,000–44,000 年

3b 49,000–44,000 ya

巴布亚人和澳大利亚人

Papuans and Australians

丹尼索瓦人 + 现代人类

Denisovans + modern humans

第四章

CHAPTER 4

4a 19,000–14,000 年

4a 19,000–14,000 ya

马格德林扩张

Magdalenian expansion

奥里尼亚克+格拉维特血统

Aurignacian + Gravettian lineages

4b >14,000 年

4b >14,000 ya

近东晚期狩猎采集者

Late Near Eastern hunter-gatherers

欧亚大陆早期人群 + 近东早期狩猎采集者

Basal Eurasians + early Near Eastern hunter-gatherers

4c ~14,000 年

4c ~14,000 ya

博林-阿勒罗德扩张

Bølling-Allerød expansion

西南欧和东南欧的狩猎采集者

Southwest + Southeast European hunter-gatherers

4天8,000–3,000年

4d 8,000–3,000 ya

近东铜器时代和青铜时代

Copper and Bronze Age Near East

伊朗、黎凡特和安纳托利亚的农民

Iranian + Levantine + Anatolian farmers

第五章

CHAPTER 5

5a 9,000–5,000 年

5a 9,000–5,000 ya

第一批欧洲农民

First European farmers

当地狩猎采集者 + 安纳托利亚农民

Local hunter-gatherers + Anatolian farmers

5b 9,000–5,000 年

5b 9,000–5,000 ya

草原牧民

Steppe pastoralists

伊朗农民 + 当地狩猎采集者

Iranian farmers + local hunter-gatherers

5c 5,000–4,000 年

5c 5,000–4,000 ya

北欧青铜时代

Northern European Bronze Age

东欧农民

Eastern European farmers

+草原牧民

+ steppe pastoralists

5天>3,500年

5d >3,500 ya

爱琴海青铜时代

Aegean Bronze Age

伊朗农民 + 欧洲农民

Iranian farmers + European farmers

5e 3,500 年至今

5e 3,500 ya – present

当代欧洲人

Present-day Europeans

北欧和南欧青铜时代人口

Northern + Southern European Bronze Age populations

第六章

CHAPTER 6

6a >4,000 年

6a >4,000 ya

南印度祖先

Ancestral South Indians

伊朗农民 + 本土

Iranian farmers + indigenous

印度狩猎采集者

Indian hunter-gatherers

6b 4,000–3,000 年

6b 4,000–3,000 ya

北印度祖先

Ancestral North Indians

草原牧民 + 伊朗农民

Steppe pastoralists + Iranian farmers

6c 4,000–2,000 年

6c 4,000–2,000 ya

当代印度人

Present-day Indians

南印度祖先 + 北印度祖先

Ancestral South Indians + Ancestral North Indians

第七章

CHAPTER 7

7a >15,000 年

7a >15,000 ya

第一批美国人

First Americans

古代北欧亚人 + 东亚人

Ancient North Eurasians + East Asians

7b 5,000–4,000 年前

7b 5,000–4,000 ya

古爱斯基摩人

Paleo-Eskimos

远东西伯利亚人 + 第一批美国人

Far Eastern Siberians + First Americans

7c >4,000 年

7c >4,000 ya

亚马逊人

Amazonians

Y人口+第一批美国人

Population Y + First Americans

7天2,000–1,000年

7d 2,000–1,000 ya

纳-德内语系

Na-Dene speakers

古爱斯基摩人 + 第一批美国人

Paleo-Eskimos + First Americans

7e 2,000–1,000 年

7e 2,000–1,000 ya

新爱斯基摩人

Neo-Eskimos

远东西伯利亚人 + 第一批美国人

Far Eastern Siberians + First Americans

第八章

CHAPTER 8

8a 5,000–4,000年前南亚语系使用者

8a 5,000–4,000 ya Austroasiatic speakers

长江幽灵人口 + 东南亚土著狩猎采集者

Yangtze River Ghost Population + indigenous Southeast Asian hunter-gatherers

8b 5,000–3,000 年

8b 5,000–3,000 ya

藏族人

Tibetans

黄河幽灵人口 + 藏族狩猎采集者

Yellow River Ghost Population + Tibetan hunter-gatherers

公元前5000年至1000年 今汉族

8c 5,000–1,000 ya Present-day Han Chinese

黄河和长江沿岸的幽灵人口

Yellow + Yangtze River Ghost Populations

8d 4,000–1,000 年

8d 4,000–1,000 ya

西南太平洋岛民

Southwest Pacific islanders

巴布亚人 + 东亚人

Papuans + East Asians

8e 3,000–2,000 ya现代日本人

8e 3,000–2,000 ya Present-day Japanese

大陆农民 + 当地狩猎采集者

Mainland farmers + local hunter-gatherers

第九章

CHAPTER 9

9a >8,000 年

9a >8,000 ya

马拉维狩猎采集者

Malawi hunter-gatherers

东非和南非的觅食者

East + South African foragers

9b 4,000–1,000 年

9b 4,000–1,000 ya

班图扩张

Bantu expansion

喀麦隆人口来源地 + 东非和南部非洲各地的当地群体

Cameroon source population + local groups throughout eastern and southern Africa

9c >3,000 年

9c >3,000 ya

东非牧民

East African pastoralists

黎凡特农民 + 东非采集者

Levantine farmers + East African foragers

9天>2,000年

9d >2,000 ya

当今西非人

Present-day West Africans

至少有两个古老的非洲血统

At least two ancient African lineages

9e 2,000–1,000 年

9e 2,000–1,000 ya

现代科伊-夸迪牧民

Present-day Khoe-Kwadi herders

东非牧民 + 土著桑人

East African pastoralists + indigenous San

致谢

Acknowledgments

首先要说明的是，这本书是我和妻子尤金妮·赖希（Eugenie Reich）一年密切合作的成果。我们一起进行研究，共同撰写章节初稿，并在创作过程中不断讨论完善。没有她，这本书根本不可能问世。

First thing first. This book emerged out of a year of intense collaboration with my wife, Eugenie Reich. We researched the book together, prepared the first drafts of the chapters together, and talked about the book incessantly as it matured. This book would not have come into being without her.

我衷心感谢 Bridget Alex、Peter Bellwood、Samuel Fenton-Whittet、Henry Louis Gates Jr.、Yonatan Grad、Iosif Lazaridis、Daniel Lieberman、Shop Mallick、Erroll McDonald、Latha Menon、Nick Patterson、Molly Przeworski、Juliet Samuel、Clifford Tabin、Daniel Reich、Tova Reich、Walter Reich、Robert Weinberg 和 Matthew Spriggs 对本书的细致批判性阅读。

I am grateful to Bridget Alex, Peter Bellwood, Samuel Fenton-Whittet, Henry Louis Gates Jr., Yonatan Grad, Iosif Lazaridis, Daniel Lieberman, Shop Mallick, Erroll McDonald, Latha Menon, Nick Patterson, Molly Przeworski, Juliet Samuel, Clifford Tabin, Daniel Reich, Tova Reich, Walter Reich, Robert Weinberg, and Matthew Spriggs for close critical readings of the entire book.

感谢 David Anthony、Ofer Bar-Yosef、Caroline Bearsted、Deborah Bolnick、Dorcas Brown、Katherine Brunson、Qiaomei Fu、David Goldstein、Alexander Kim、Carles Lalueza-Fox、Iain Mathieson、Eric Lander、Mark Lipson、Scott MacEachern、Richard Meadow、David Meltzer、Priya Moorjani、John Novembre、Svante Pääbo、Pier Palamara、Eleftheria Palkopoulou、Mary Prendergast、Rebecca Reich、Colin Renfrew、Nadin Rohland、Daniel Rozas、Pontus Skoglund、Chuanchao Wang 和 Michael Witzel 对各章节提出的批评意见。我还要感谢 Stanley Ambrose、Graham Coop、Dorian Fuller、Éadaion Harney、Linda Heywood、Yousuke Kaifu、Kristian Kristiansen、Michelle Lee、Daniel Lieberman、Michael McCormick、Michael Petraglia、Joseph Pickrell、Stephen Schiffels、Beth Shapiro 和 Bence Viola 对本书部分内容的准确性进行了审阅。

I thank David Anthony, Ofer Bar-Yosef, Caroline Bearsted, Deborah Bolnick, Dorcas Brown, Katherine Brunson, Qiaomei Fu, David Goldstein, Alexander Kim, Carles Lalueza-Fox, Iain Mathieson, Eric Lander, Mark Lipson, Scott MacEachern, Richard Meadow, David Meltzer, Priya Moorjani, John Novembre, Svante Pääbo, Pier Palamara, Eleftheria Palkopoulou, Mary Prendergast, Rebecca Reich, Colin Renfrew, Nadin Rohland, Daniel Rozas, Pontus Skoglund, Chuanchao Wang, and Michael Witzel for critiques of individual chapters. I also thank Stanley Ambrose, Graham Coop, Dorian Fuller, Éadaion Harney, Linda Heywood, Yousuke Kaifu, Kristian Kristiansen, Michelle Lee, Daniel Lieberman, Michael McCormick, Michael Petraglia, Joseph Pickrell, Stephen Schiffels, Beth Shapiro, and Bence Viola for reviewing sections of the book for accuracy.

我衷心感谢哈佛医学院、霍华德·休斯医学研究所和国家科学基金会，在我从事这项研究期间，他们都慷慨地支持了我的科学研究，并将这项研究视为对我主要研究的补充。

I am grateful to Harvard Medical School, the Howard Hughes Medical Institute, and the National Science Foundation, all of which generously supported my science while I was working on this project, and viewed it as complementary to my primary research.

最后，我要感谢几位反复鼓励我写这本书的人。多年来，我一直抗拒这个想法，因为我不想让自己的科研工作分心，而且对遗传学家来说，论文才是硬通货，而不是书籍。但随着我的同事越来越多，包括考古学家、人类学家、历史学家、语言学家以及其他渴望深入了解古代DNA革命的学者，我的想法也发生了改变。由于写作本书需要大量时间，我错过了许多论文的撰写和分析。我希望读者读完本书后，能够对我们自身产生新的认识。

I finally thank several people who repeatedly encouraged me to write this book. I resisted the idea for years because I did not want to distract myself from my science, and because for geneticists papers are the currency, not books. But my mind changed as my colleagues grew to include archaeologists, anthropologists, historians, linguists, and others eager to come to grips with the ancient DNA revolution. There are many papers I did not write, and many analyses I did not complete, because of the time I needed to write this book. I hope that those who read the book will emerge with a new perspective on who we are.

介绍

Introduction

本书的灵感源自一位富有远见的先驱——卢卡·卡瓦利-斯福尔扎，他是人类历史遗传学研究的奠基人。我曾师从他的一位学生，因此，我算是他的学派的一员，深受他关于基因组是理解我们物种历史的棱镜这一理念的启发。

This book is inspired by a visionary, Luca Cavalli-Sforza, the founder of genetic studies of our past. I was trained by one of his students, and so it is that I am part of his school, inspired by his vision of the genome as a prism for understanding the history of our species.

卡瓦利-斯福尔扎的职业生涯巅峰之作是1994年出版的《人类基因的历史与地理》。该书综合了当时考古学、语言学、历史学和遗传学领域的知识，^讲述了一个关于世界人类如何演变成今天模样的宏大故事。¹这本书概述了遥远的过去。但由于当时遗传数据的匮乏，它受到了限制。当时的遗传数据非常有限，与考古学和语言学领域更为丰富的信息相比几乎毫无用处。当时的遗传数据有时能够揭示与已知相符的模式，但提供的信息不足以证明任何真正的新发现。事实上，卡瓦利-斯福尔扎提出的少数几个重要新论断几乎都被证明是错误的。二十年前，从卡瓦利-斯福尔扎到像我这样的研究生，所有人都处于DNA研究的黑暗时代。

The high-water mark of Cavalli-Sforza’s career came in 1994 when he published The History and Geography of Human Genes, which synthesized what was then known from archaeology, linguistics, history, and genetics to tell a grand story about how the world’s peoples got to be the way they are today.¹ The book offered an overview of the deep past. But it was based on what was known at the time and was therefore handicapped by the paucity of genetic data then available, which were so limited as to be nearly useless compared to the far more extensive information from archaeology and linguistics. The genetic data of the time could sometimes reveal patterns consistent with what was already known, but the information they provided were not rich enough to demonstrate anything truly new. In fact, the few major new claims that Cavalli-Sforza did make have essentially all been proven wrong. Two decades ago, everyone, from Cavalli-Sforza to beginning graduate students such as myself, was working in the dark ages of DNA.

1960年，卡瓦利-斯福尔扎做出了一个大胆的赌注，这个赌注贯穿了他整个职业生涯。他认为，完全根据现代人群之间的基因差异，就有可能重建过去的大规模人口迁徙^。

Cavalli-Sforza made a grand bet in 1960 that would drive his entire career. He bet that it would be possible to reconstruct the great migrations of the past based entirely on the genetic differences among present-day peoples.²

在随后的五十年里，卡瓦利-斯福尔扎通过一项又一项的研究，似乎正朝着实现他的预言稳步前进。在他开始这项研究时，研究人类变异的技术还非常落后，唯一的办法是测量血液中的蛋白质，利用诸如A、B、O等血型（医生用这些血型来匹配献血者和受血者）之类的变异。到了20世纪90年代，他和他的同事们已经收集了来自不同人群的一百多种此类变异的数据。利用这些数据，他们能够根据个体在这些变异上的匹配频率，可靠地按洲对个体进行聚类：例如，欧洲人与其他欧洲人的匹配率很高，东亚人与东亚人的匹配率很高，非洲人与非洲人的匹配率很高。在20世纪90年代和21世纪初，他们将研究提升到了一个新的水平，不再局限于蛋白质变异，而是直接研究DNA——我们的遗传密码。他们分析了来自全球约50个不同人群的约1000名个体，研究了基因组中300多个位点的变异。³当他们告诉计算机（计算机对人口标签一无所知）将个体聚类成五组时，结果与人们对人类深层祖先划分的普遍直觉（西欧亚人、东亚人、美洲原住民、新几内亚人和非洲人）惊人地吻合。

Through study after study over the subsequent five decades, Cavalli-Sforza seemed to be well on the path to making good on his bet. When he started his work, the technology for studying human variation was so poor that the only possibility was to measure proteins in the blood, using variations like the A, B, and O blood types that are tested by physicians to match blood donors to recipients. By the 1990s, he and his colleagues had assembled data from more than one hundred such variations in diverse populations. Using these data they were able to reliably cluster individuals by continent based on how often they matched each other at these variations: for example, Europeans have a high rate of matching to other Europeans, East Asians to East Asians, and Africans to Africans. In the 1990s and 2000s, they brought their work to a new level by moving beyond protein variation and directly examining DNA, our genetic code. They analyzed a total of about one thousand individuals from around fifty populations spread across the planet, examining variation at more than three hundred positions in the genome.³ When they told their computer—which had no knowledge of the population labels—to cluster the individuals into five groups, the results corresponded uncannily well to commonly held intuitions about the deep ancestral divisions among humans (West Eurasians, East Asians, Native Americans, New Guineans, and Africans).

卡瓦利-斯福尔扎尤其感兴趣的是从人口历史的角度解读现代人群的基因簇。他和同事们运用一种能够识别最有效地概括个体差异的生物变异组合的技术，分析了他们的血型数据。他们将这些血型组合绘制在西欧亚大陆的地图上，发现概括个体差异最大的组合在近东地区达到极值，并沿着东南至西北的梯度向欧洲递减。他们^将此解释为近东农民迁徙到欧洲的遗传印记，考古学表明，这一迁徙发生在九千年前。这种强度递减的趋势表明，第一批农民抵达欧洲后，与当地的狩猎采集者融合，随着迁徙范围的扩大，他们积累了更多的狩猎采集者血统，这一过程被他们称为“流行扩散” ^。最近，许多考古学家将人口扩散模型视为考古学和遗传学见解的典范融合。

Cavalli-Sforza was especially interested in interpreting the genetic clusters among present-day people in terms of population history. He and his colleagues analyzed their blood group data by using a technique that identifies combinations of biological variations that are most efficient at summarizing differences across individuals. Plotting these combinations of blood group types onto a map of West Eurasia, they found that the one summarizing the most variation across individuals reached its extreme value in the Near East, and declined along a southeast-to-northwest gradient into Europe.⁴ They interpreted this as a genetic footprint of the migration of farmers into Europe from the Near East, known from archaeology to have occurred after nine thousand years ago. The declining intensity suggested to them that after arriving in Europe, the first farmers mixed with local hunter-gatherers, accumulating more hunter-gatherer ancestry as they expanded, a process they called “demic diffusion.”⁵ Until recently, many archaeologists viewed the demic diffusion model as an exemplary merging of insights from archaeology and genetics.

Cavalli-Sforza及其同事提出的用于描述数据的模型在理论上很有吸引力，但却是错误的。该模型的缺陷从2008年开始显现，当时John Novembre及其同事证明，类似欧洲观测到的梯度现象可以在没有人口迁移的情况下出现。 ⁶他们随后指出，近东农业向欧洲的扩张可能会反直觉地导致Cavalli-Sforza所使用的数学方法所推导出的梯度现象，该梯度现象垂直于人口迁移方向，而非像实际数据中观察到的那样平行于迁移方向。 ⁷

The model that Cavalli-Sforza and colleagues proposed to describe the data was intellectually attractive, but it was wrong. Its flaws became apparent beginning in 2008, when John Novembre and colleagues demonstrated that gradients like those observed in Europe can arise without migration.⁶ They then showed that a Near Eastern farming expansion into Europe might counter-intuitively cause the mathematical technique that Cavalli-Sforza used to produce a gradient perpendicular to the direction of migration, not parallel to it as had been seen in the real data.⁷

从古代骨骼中提取DNA的能力所带来的革命性变革——“古代DNA革命”——彻底终结了人口扩散模型。古代DNA革命证实，即使在欧洲最偏远的地区——英国、斯堪的纳维亚和伊比利亚半岛——最早的农民也几乎没有狩猎采集者的血统。事实上，他们的狩猎采集者血统比例甚至低于当今欧洲不同人群的比例。如今，欧洲早期农民血统比例最高的地区并非卡瓦利-斯福尔扎根据血型数据认为的东南欧，而是意大利西部的撒丁岛。 ⁸

It took the revolution wrought by the ability to extract DNA from ancient bones—the “ancient DNA revolution”—to drive a nail into the coffin of the demic diffusion model. The ancient DNA revolution documented that the first farmers even in the most remote reaches of Europe—Britain, Scandinavia, and Iberia—had very little hunter-gatherer-related ancestry. In fact, they had less hunter-gatherer ancestry than is present in diverse European populations today. The highest proportion of early farmer ancestry in Europe is today not in Southeast Europe, the place where Cavalli-Sforza thought it was most common based on the blood group data, but instead is in the Mediterranean island of Sardinia to the west of Italy.⁸

卡瓦利-斯福尔扎的地图示例说明了斯福尔扎的宏伟赌注为何失败。他关于当今人口遗传结构反映了人类历史上一些重大事件的假设是正确的。例如，与非洲人相比，非非洲人的遗传多样性较低，这反映了大约五万年前从非洲和近东扩张出来的现代人类群体的遗传多样性降低。但是，当今的人口结构无法重现古代事件的精细细节。问题不仅仅在于人们与邻近人群通婚，模糊了过去事件的遗传特征。实际上，情况要复杂得多，因为我们现在从古代DNA中得知，今天生活在特定地区的人几乎不可能完全是过去生活在同一地区的人的后裔。在^这种情况下，任何试图根据当今人口重建过去人口迁徙的研究都存在局限性。在《人类基因的历史与地理》一书中，卡瓦利-斯福尔扎写道，他将已知由大规模迁徙产生的群体排除在分析之外，例如美洲的欧洲和非洲裔群体，他们的起源可追溯到过去五百年间的跨大西洋迁徙，以及罗姆人和犹太人等欧洲少数族裔。他认为，过去远比现在简单得多，通过关注那些在其有记载的历史中未受大规模迁徙影响的群体，他或许能够研究到很久以前生活在同一地区的人们的直系后裔。然而，对古代DNA的研究表明，过去并不比现在简单。人类群体一直在不断更迭。

The example of Cavalli-Sforza’s maps shows why his Sforza’s grand bet went sour. He was correct in his assumption that the present-day genetic structure of populations echoes some of the great events in the human past. For example, the lower genetic diversity of non-Africans compared to Africans reflects the reduced diversity of the modern human population that expanded out of Africa and the Near East after around fifty thousand years ago. But the present-day structure of human populations cannot recover the fine details of ancient events. The problem is not just that people have mixed with their neighbors, blurring the genetic signatures of past events. It is actually far more difficult, in that we now know, from ancient DNA, that the people who live in a particular place today almost never exclusively descend from the people who lived in the same place far in the past.⁹ Under these circumstances, the power of any study that attempts to reconstruct past population movements from present-day populations is limited. In The History and Geography of Human Genes, Cavalli-Sforza wrote that he was excluding from his analysis populations known to be the product of major migrations, such as those of European and African ancestry in the Americas that owe their origin to transatlantic migrations in the last five hundred years, or European minorities such as Roma and Jews. His bet was that the past was a much simpler place than the present, and that by focusing on populations today that are not affected by major migrations in their recorded history, he might be studying direct descendants of people who lived in the same places long before. But what the study of ancient DNA has now shown is that the past was no less complicated than the present. Human populations have repeatedly turned over.

卡瓦利-斯福尔扎对人类史前遗传学研究领域的变革性贡献，令人想起摩西的故事。摩西是一位富有远见的领袖，他的成就超越了所有后继者，并为世人树立了看待世界的新典范。《圣经》记载：“以色列再也没有兴起像摩西那样的先知”，但也讲述了摩西未能进入应许之地的故事。在带领以色列人在旷野跋涉四十年后，摩西登上尼波山，向西眺望约旦河，看到了应许之地。但他却被禁止进入。这份特权留给了他的继任者。

Cavalli-Sforza’s transformative contribution to the field of genetic studies of human prehistory recalls the story of Moses, a visionary leader whose achievement was greater than that of anyone who followed him and who created a new template for seeing the world. The Bible says, “No prophet ever arose again in Israel like Moses,” but also tells how Moses was not allowed to reach the promised land. After leading his people for forty years through the wilderness, Moses climbed the mountain of Nebo and looked west over the Jordan River to see the land his people had been promised. But he was not allowed to enter that land. That privilege had been reserved for his successors.

对过去进行基因研究也是如此。卡瓦利-斯福尔扎比任何人都更早地看到了基因学在揭示人类历史方面的全部潜力，但他的远见卓识早于实现这一愿景所需的技术。然而，如今情况已大不相同。我们拥有数百个……我们拥有千倍的数据量，此外，我们还可以获取古代 DNA 中蕴含的丰富信息，这已成为比考古学和语言学等传统工具更确凿的有关过去人口迁徙的信息来源。

So it is with genetic studies of the past. Cavalli-Sforza saw before anyone else the full potential of genetics for revealing the human past, but his vision predated the technology needed to fulfill it. Today, however, things are very different. We have several hundred thousand times more data, and in addition we have access to the rich lode of information contained in ancient DNA, which has become a more definitive source of information about past population movements than the traditional tools of archaeology and linguistics.

首批五个古代人类基因组于2010年发表：几个古老的尼安德特人基因组 ¹⁰ 、古老的丹尼索瓦人基因组 ¹¹ ，以及一个来自格陵兰岛、距今约四千年的个体 ¹² 。接下来的几年里，又有五个人类的全基因组数据发表，随后在2014年，来自38个个体的全基因组数据激增。但到了2015年，古代DNA的全基因组分析进入了高速发展阶段。三篇论文分别补充了来自另外66个13、¹⁰⁰个 ¹⁴和83个 ¹⁵ 样本的全基因组数据集。到2017年8月，仅我的实验室就生成了超过3000个古代样本的全基因组数据。我们现在的数据生成速度如此之快，以至于数据生成到发表之间的时间间隔比野外数据翻倍所需的时间还要长。

The first five ancient human genomes were published in 2010: a few archaic Neanderthal genomes,¹⁰ the archaic Denisova genome,¹¹ and an approximately four-thousand-year-old individual from Greenland.¹² The next few years saw the publication of genome-wide data from five additional humans, followed by a burst of data from thirty-eight individuals in 2014. But in 2015, whole-genome analysis of ancient DNA went into hyperdrive. Three papers added genome-wide datasets from another sixty-six,¹³ then one hundred,¹⁴ and then eighty-three samples.¹⁵ By August 2017, my laboratory alone had generated genome-wide data for more than three thousand ancient samples. We are now producing data so fast that the time lag between data production and publication is longer than the time it takes to double the data in the field.

全基因组古DNA革命的大部分技术是由德国莱比锡马克斯·普朗克进化人类学研究所的斯万特·帕博及其同事发明的，他们最初开发这些技术是为了研究极其古老的样本，例如尼安德特人和丹尼索瓦人。我的贡献在于将这些方法扩展到研究大量相对较近的样本，尽管这些样本仍然有数千年的历史。传统的学徒期为七年，我的学徒期始于2007年，当时我开始与帕博合作开展尼安德特人和丹尼索瓦人的基因组项目。2013年，帕博帮助我建立了自己的古DNA实验室——这是美国第一个专注于研究全基因组古人类DNA的实验室。我的合作伙伴是纳丁·罗兰，她也完成了自己为期七年的学徒期。在她来我实验室之前，她曾在帕博的实验室当过学徒。我们的想法是让古代DNA产业化——利用欧洲开发的用于研究个体样本的技术，建立一个美式基因组学工厂。

Much of the technology for the genome-wide ancient DNA revolution was invented by Svante Pääbo and his colleagues at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who developed it to study extremely old samples such as archaic Neanderthals and Denisovans. My contribution has been to scale up the methods to study large numbers of relatively more recent samples, albeit still many thousands of years old. The traditional length of an apprenticeship is seven years, and I began mine in 2007 when I started working with Pääbo on the Neanderthal and Denisova genome projects. In 2013, Pääbo helped me to establish my own ancient DNA laboratory—the first in the United States focused on studying whole-genome ancient human DNA. My partner in this effort has been Nadin Rohland, who did her own seven-year apprenticeship in Pääbo’s laboratory before she came to mine. Our idea was to make ancient DNA industrial—to build an American-style genomics factory out of the techniques developed in Europe to study individual samples.

罗兰德和我意识到，马蒂亚斯·迈耶和傅巧梅在帕博实验室开发的一项技术可能是大规模研究古代DNA的关键。迈耶和傅巧梅的发明源于实际需要：他们需要从中国天元洞中一具距今约四万年的早期现代人类遗骸中提取DNA。 ¹⁶当迈耶和傅巧梅从天元洞的腿骨中提取DNA时，他们发现其中只有约0.02%来自洞主本人。其余的则来自洞主死后在其骨骼上定植的微生物。这使得直接测序成本过高，即使使用2006年左右之后出现的成本降低十万倍的技术也无济于事。为了克服这一难题，迈耶和傅巧梅借鉴了医学遗传学家开发的方法。正如医学遗传学家开发出从基因组中最有趣的 2% 中分离出 DNA 并丢弃其余 98% 的方法一样，迈耶和傅从天元骨中分离出一小部分人类序列，并丢弃了其余部分。

Rohland and I realized that a technique developed by Matthias Meyer and Qiaomei Fu in Pääbo’s laboratory could be the key to the industrial-scale study of ancient DNA. Meyer and Fu’s invention was born of necessity: the need to extract DNA from an approximately forty-thousand-year-old early modern human from Tianyuan Cave in China.¹⁶ When Meyer and Fu extracted DNA from Tianyuan’s leg bones, they found that only about 0.02 percent of it was from the man himself. The rest came from microbes that had colonized his bones after he died. This made direct sequencing too expensive, even using the hundred-thousand-times cheaper technology that had become available after around 2006. To get around this challenge, Meyer and Fu borrowed a page from the playbook of methods developed by medical geneticists. Just as medical geneticists had developed methods to isolate DNA from the 2 percent of the genome that is most interesting and to discard the other 98 percent, Meyer and Fu isolated a tiny fraction of sequences from the Tianyuan bone that were human and discarded the rest.

迈耶和傅氏开发的DNA分离方法是古代DNA革命成功的关键。20世纪90年代，分子生物学家学会了如何利用激光蚀刻技术（该技术最初用于印刷电子电路）将数百万条他们选择的DNA序列附着到硅或玻璃晶片上。然后，他们可以使用分子剪刀（酶）将这些序列从晶片上切割下来，并释放到水溶液中。迈耶和傅氏利用这种方法合成了52个碱基对长的DNA序列，这些序列像屋顶上的瓦片一样相互重叠，覆盖了人类21号染色体的大部分区域。他们利用DNA倾向于与高度相似的序列结合的特性，以人工合成的序列为“诱饵”，从天元身上“钓取”出他们感兴趣的DNA序列。他们发现，他们获得的DNA中有很大一部分来自天元的基因组。不仅如此，这些DNA还来自天元基因组中他们想要研究的部分。他们分析了数据，结果表明天元……他是早期现代人类，属于现代东亚人的祖先谱系的一部分。他并没有大量来自与现代人类谱系分化数十万年的古老人类谱系的血统，这与之前基于其骨骼形状的论断相矛盾。 ¹⁷

The method of DNA isolation that Meyer and Fu developed has been central to the success of the ancient DNA revolution. In the 1990s, molecular biologists learned how to adapt laser-etching techniques invented for printing electronic circuits to attach millions of DNA sequences of their choice to silicon or glass wafers. These sequences could then be cut off the wafers using molecular scissors (enzymes) and released into a watery mix. Meyer and Fu took advantage of this method to synthesize fifty-two-letter-long sequences of DNA that, overlapping like shingles on a roof, covered much of human chromosome 21. Exploiting DNA’s tendency to bind to highly similar sequences, they “fished” out the DNA sequences from Tianyuan that they were interested in by using as “bait” the sequences they had artificially synthesized. They found that a large fraction of the DNA they obtained was from Tianyuan’s genome. Not only that, but it was from the parts of Tianyuan’s genome that they wanted to study. They analyzed the data to show that Tianyuan was an early modern human, part of the lineage leading to present-day East Asians. He did not have a particularly large amount of ancestry from archaic human lineages that were diverged by hundreds of thousands of years from modern human lineages, contradicting earlier claims based on the shape of his skeleton.¹⁷

我和罗兰德将这项技术应用于全基因组研究。我们与德国的同事合作，合成了52个碱基长度的DNA序列，这些序列覆盖了已知人类基因组中存在变异的一百万多个位点。我们利用这些诱饵序列来富集人类DNA，使其高于微生物DNA，在某些情况下，这使我们感兴趣的DNA比例提高了百倍以上。由于我们只针对基因组中的信息位点，效率又提高了约十倍。我们实现了整个流程的自动化，利用机器人处理DNA，使得一个人能够在几天内同时研究超过90个样本。我们聘请了一支技术团队，将古代遗骸研磨成粉末，从中提取DNA，然后将提取的DNA转化为我们可以测序的形式。实验室工作仅仅是开始。同样复杂的任务是将数十亿条DNA序列归类到它们所属的个体，分析数据，剔除有污染迹象的样本，并创建一个易于访问的数据集。六年前加入我实验室的物理学家肖普·马利克设置了我们的计算机来完成所有这些工作，并且随着数据性质的演变和数据的增加，不断更新我们处理数据的策略。

Rohland and I adapted this technique to study the whole genome. We worked with our colleagues in Germany to synthesize fifty-two-letter-long DNA sequences covering more than a million positions at which people are known to vary. We used these bait sequences to enrich for human compared to microbial DNA, which in some cases increased the fraction of DNA that was of interest to us by more than a hundredfold. We gained another approximately tenfold jump in efficiency because we only targeted informative positions in the genome. We automated the whole approach, processing the DNA using robots that allowed a single person to study more than ninety samples at once in the span of a few days. We hired a team of technicians to grind powder out of ancient remains, to extract DNA from the powder, and then to turn the extracted DNA into a form that we could sequence. The laboratory work was only the beginning. An equally intricate task was sorting the billions of DNA sequences into the individuals to whom they belonged, analyzing the data and weeding out samples with evidence of contamination, and creating an easily accessible dataset. Shop Mallick, a physicist who had joined my laboratory six years before, set up our computers to do all of this, and continually updated our strategy for processing the data as the nature of the data evolved and its volume increased.

结果甚至比我们预期的还要好。每个样本的全基因组数据生成成本降至不到五百美元。这比传统的粗略全基因组测序便宜几十倍。更令人欣喜的是，我们的方法能够从大约一半的骨骼样本中获得全基因组数据，当然，成功率会根据骨骼的保存程度而有所不同。例如，对于来自俄罗斯寒冷气候地区的古代样本，我们的成功率约为75%，而对于来自近东炎热气候地区的样本，成功率仅为30%左右。

The results were even better than we had hoped. The cost of producing genome-wide data dropped to less than five hundred dollars per sample. This was many dozens of times cheaper than brute-force whole-genome sequencing. Even better, our method made it possible to get genome-wide data out of around half of the skeletal samples we screened, although the success rate of course varied depending on the degree to which the skeletons we examined had been preserved. For example, we have obtained about 75 percent success rates for ancient samples from the cold climate of Russia, but only around 30 percent for samples from the hot Near East.

这些进展意味着对古代DNA进行全基因组研究如今，无需再像过去那样筛选大量骨骼遗骸才能找到少数可进行DNA分析的个体。相反，过去一万年间筛选出的样本中，相当一部分现在可以转化为可用的全基因组数据。这些新方法使得在单项研究中分析数百个样本成为可能。有了这些数据，我们就能极其细致地重建人口变迁，从而彻底改变我们对过去的认知。

These advances mean that whole-genome study of ancient DNA no longer requires screening large numbers of skeletal remains before it is possible to find a few individuals whose DNA can be analyzed. Instead, a substantial fraction of screened samples dating to the last ten thousand years can now be converted to working genome-wide data. The new methods have made it possible to analyze hundreds of samples in a single study. With such data, it is possible to reconstruct population changes in exquisite detail, transforming our understanding of the past.

到2015年底，我在哈佛大学的古DNA实验室已经发表了全球一半以上的人类古DNA全基因组数据。我们发现，五千年前，北欧人口基本被来自东欧草原的大规模迁徙所取代 ¹⁸ ；农业在一万多年前的近东地区发展起来，当时存在着多个高度分化的人类群体，随着农业的传播，这些群体向四面八方扩张并相互融合 ¹⁹；大约三千年前开始迁徙到偏远太平洋岛屿的第一批人类并非当今居民的唯一祖先 ²⁰ 。与此同时，我启动了一个项目，旨在调查当今世界人口的多样性。该项目使用了一种由我和我的合作者专门为研究人类历史而设计的微芯片来分析人类变异。我们利用该芯片研究了来自全球一千多个群体的一万多名个体——这一数据集不仅成为我实验室，也成为世界各地其他实验室研究人类变异的重要基础。²¹

By the end of 2015, my ancient DNA laboratory at Harvard had published more than half of the world’s genome-wide human ancient DNA. We discovered that the population of northern Europe was largely replaced by a mass migration from the eastern European steppe after five thousand years ago¹⁸; that farming developed in the Near East more than ten thousand years ago among multiple highly differentiated human populations that then expanded in all directions and mixed with each other along with the spread of agriculture¹⁹; and that the first human migrants into the remote Pacific islands beginning around three thousand years ago were not the sole ancestors of the present-day inhabitants.²⁰ In parallel, I initiated a project to survey the diversity of the world’s present-day populations, using a microchip for analyzing human variation that my collaborators and I designed specifically for the purpose of studying the human past. We used the chip to study more than ten thousand individuals from more than a thousand populations worldwide—a dataset that has become a mainstay of studies of human variation not just in my laboratory but also in other laboratories around the world.²¹

这场革命让我们能够如此精确地重构人类历史事件，其程度令人惊叹。我记得研究生毕业时，曾与我的博士生导师大卫·戈德斯坦（David Goldstein）和他的妻子卡维塔·纳亚尔（Kavita Nayar）共进晚餐，他们两人都曾是卡瓦利-斯福尔扎（Cavalli-Sforza）的学生。那是1999年，全基因组古DNA技术问世前十年，我们一起畅想，究竟能通过遗留的痕迹多精确地重构过去的事件。例如，如果房间里发生了一起手榴弹爆炸，我们能否通过拼凑散落的残骸并研究其中的弹片，来还原爆炸前每个物体的确切位置？一堵墙？能否通过打开一个至今仍回荡着数千年前人们所说话语回响的洞穴，来重现早已消亡的语言？如今，古DNA技术正使我们能够详细重建古代人类群体之间的深层关系。

The resolution with which this revolution has allowed us to reconstruct events in the human past is stunning. I remember a dinner at the end of graduate school with my Ph.D. supervisor, David Goldstein, and his wife, Kavita Nayar, both of whom had been students of Cavalli-Sforza. It was 1999, a decade before the advent of genome-wide ancient DNA, and we daydreamed together, wondering how accurately events of the past could be reconstructed by traces left behind. After a grenade explosion in a room, could the exact position of each object prior to the explosion be reconstructed by piecing together the scattered remains and studying the shrapnel in the wall? Could languages long extinct be recalled by unsealing a cave still reverberating with the echoes of words spoken there thousands of years ago? Today, ancient DNA is enabling this kind of detailed reconstruction of deep relationships among ancient human populations.

如今，人类基因组变异在揭示远古时期人类群体变迁方面，已经超越了传统的考古工具——即研究古代社会遗留的文物。 ²²这几乎让所有人都感到惊讶。《 纽约时报》的科学记者卡尔·齐默经常撰写有关这一新兴领域的文章。他告诉我，当报社指派他报道古代DNA研究时，他只是出于对科研团队的帮助而答应，认为这只是他主要关注的进化和人类生理学之外的一个次要领域。他设想自己大约每六个月写一篇关于这个领域的文章，而且一两年后，新发现的浪潮就会消退。然而，齐默现在发现自己几乎每隔几周就要面对一篇重要的科学论文，而且研究进展还在加速，这场革命也在不断加剧。

These days, human genome variation has surpassed the traditional toolkit of archaeology—the study of the artifacts left behind by past societies—in what it can reveal of changes in human populations in the deep past.²² This has come as a surprise to nearly everyone. Carl Zimmer, a science journalist at The New York Times who has written frequently about this new field, told me that when he was assigned by his newspaper to cover the study of ancient DNA, he agreed to do it as a service to the science team, thinking it would be a minor sideshow to his main focus on evolution and human physiology. He imagined writing an article about the field every six months or so, and that the rush of discoveries would end after a year or two. Instead, Zimmer now finds himself dealing with a major new scientific paper every few weeks, even as developments are accelerating and the revolution intensifies.

本书讲述的是基因组革命在人类历史研究中的兴起。这场革命源于基于全基因组数据的海量发现——也就是说，不再仅仅分析线粒体DNA等小片段基因组，而是一次性分析整个基因组。从古代人类中提取全基因组DNA的新技术极大地增强了这场革命的力量。我并不打算追溯过去遗传学研究领域的发展历程——数十年来，对人类变异的科学分析始于对骨骼变异的研究，随后扩展到对人类基因组微小片段遗传变异的研究。这些研究为了解人口关系和迁徙提供了见解，但与2009年后开始涌现的大量数据所揭示的惊人信息相比，这些见解显得黯然失色。在此之前和之后，对基因组中一个或几个位点的研究偶尔也能带来重要的发现，为某些假设提供证据，从而支持其他假设。然而，2009 年左右之前的基因证据在人类历史研究中大多是附带的。在其他领域，全基因组数据只是考古学这一主业的卑微附属品。然而，自2009年以来，全基因组数据开始挑战考古学、历史学、人类学乃至语言学领域长期以来的观点，并有助于解决这些领域的争议。

This book is about the genome revolution in the study of the human past. This revolution consists of the avalanche of discoveries based on data taken from the whole genome—meaning, the entire genome analyzed at once instead of just small stretches of it such as mitochondrial DNA. The revolution has been made far more powerful by the new technologies for extracting whole genomes’ worth of DNA from ancient humans. I make no attempt to trace the history of the field of genetic studies of the past—the decades of scientific analysis of human variation that began with studies of skeletal variation and continued with studies of genetic variation in tiny snippets of the human genome. These efforts provided insights into population relationships and migrations, but those insights pale when compared to the dazzling information provided by the extraordinary tranches of data that began to be available after 2009. Before and after that year, studies of one or a few locations in the genome were occasionally the basis for important discoveries, providing evidence in favor of some scenarios over others. Yet genetic evidence before around 2009 was mostly incidental to studies of the human past in other fields, a poor handmaiden to the main business of archaeology. Since 2009, though, whole-genome data have begun to challenge long-held views in archaeology, history, anthropology, and even linguistics—and to resolve controversies in those fields.

古DNA革命正在迅速颠覆我们对过去的固有认知。然而，目前尚无任何一位在职遗传学家撰写的书籍，能够全面阐述这项新兴科学的影响，并解释如何利用它来确立令人信服的新事实。要理解古DNA革命的全貌，所需的研究成果散落在晦涩难懂、充斥着专业术语的科学论文中，有时甚至需要数百页详尽的方法论注释来补充。在《我们是谁，我们如何走到今天》一书中，我旨在为读者提供一个清晰的视角，透过这扇通往过去的非凡窗口，为普通读者和专业人士提供一本关于古DNA革命的著作。我的目标并非进行全面总结——因为该领域的发展日新月异。当本书面世时，其中描述的一些进展可能已被取代，甚至被推翻。自从我开始写作以来的三年间，涌现出了许多新的发现，因此，本书的大部分内容都基于我开始写作之后的研究成果。我希望读者能将我讨论的话题视为全基因组研究颠覆性力量的例证，而不是对该科学现状的最终总结。

The ancient DNA revolution is rapidly disrupting our assumptions about the past. Yet there is at present no book by a working geneticist that lays out the impact of the new science and explains how it can be used to establish compelling new facts. The findings needed to grasp the scope of the ancient DNA revolution are scattered among hard-to-read, jargon-filled scientific papers, sometimes supplemented by hundreds of pages of dense notes on methodology. In Who We Are and How We Got Here, I aim to offer readers a clear view through this extraordinary window into the past—to provide a book about the ancient DNA revolution intended for lay reader and specialist alike. My goal is not to present a synthesis—the field is moving too quickly. By the time this book reaches readers, some advances that it describes will have been superseded or even contradicted. In the three years since I began writing, many fresh findings have emerged, so that most of what I describe here is based on results obtained after I started. I hope that readers will take the topics I discuss as examples of the disruptive power of whole-genome studies, not as a definitive summary of the state of the science.

我的写作方法是带领读者经历发现的过程，每一章都像一个论证，旨在引导读者——无论他们起初带着何种观点——在读完之后形成不同的视角。我力求突出我的实验室在古代DNA革命中的核心地位，在相关之处讲述我自己的工作——因为这是我拥有权威性的领域——同时也会探讨那些我未参与但对故事至关重要的研究。正因如此，本书对我的实验室的工作着墨较多。对于其他同样做出重要贡献的人，我只能提及其中极少一部分，对此我深表歉意。我的首要目标是传达基因组革命的激动人心和出乎意料之处，并带领读者踏上一段引人入胜的叙事之旅，而非撰写一篇科学评论。

My approach is to take readers through the process of discovery, with each chapter serving as an argument that has as its goal to bring readers, who may have come with one perspective when they started, to another place when they finish. I try to make a virtue of my laboratory’s central role in the ancient DNA revolution by telling the story of my own work where it is relevant—as this is a subject on which I can speak with great authority—while also discussing work in which I was not involved when it is critical to the story. Because I take this approach, the book disproportionately highlights the work from my laboratory. I apologize that I have been able to mention by name only a tiny fraction of the people who made equally important contributions. My priority has been to convey the excitement and surprise of the genome revolution, and to take readers on a compelling narrative path through it, not to write a scientific review.

我还重点介绍了一些正在涌现的重要主题，尤其值得注意的是，研究发现高度分化的人群之间的混合是人类历史上反复出现的过程。如今，许多人认为人类可以从生物学角度被划分为“原始”群体，这与我们“种族”的概念相对应，这些种族起源于数万年前分离的人群。然而，这种关于“种族”的长期观点在近几年已被证明是错误的——新数据对种族概念的批判与过去一百年来人类学家发展出的经典批判截然不同。基因组革命带来的一个巨大惊喜是，在相对较近的过去，人类群体之间的差异与今天一样大，但群体间的分界线与今天几乎完全不同。从例如一万年前人类遗骸中提取的DNA表明，当时人类群体的结构与现在截然不同。当今的人口是过去人口的混合体，而过去的人口本身也是混合体。美洲的非裔美国人和拉丁裔人口只是众多大规模人口融合中的最新例子。

I also highlight some of the great themes that are emerging, especially the finding that mixture between highly differentiated populations is a recurrent process in the human past. Today, many people assume that humans can be grouped biologically into “primeval” groups, corresponding to our notion of “races,” whose origins are populations that separated tens of thousands of years ago. But this long-held view about “race” has just in the last few years been proven wrong—and the critique of concepts of race that the new data provide is very different from the classic one that has been developed by anthropologists over the last hundred years. A great surprise that emerges from the genome revolution is that in the relatively recent past, human populations were just as different from each other as they are today, but that the fault lines across populations were almost unrecognizably different from today. DNA extracted from remains of people who lived, say, ten thousand years ago shows that the structure of human populations at that time was qualitatively different. Present-day populations are blends of past populations, which were blends themselves. The African American and Latino populations of the Americas are only the latest in a long line of major population mixtures.

《我们是谁，我们如何走到今天》分为三部分。第一部分“我们物种的深层历史”阐述了人类基因组不仅提供了受精卵发育所需的所有信息，而且还包含了我们物种的历史。第一章“基因组如何解释我们是谁”论证了基因组革命让我们了解人类的本质，并非通过揭示我们与其他动物相比的独特生物学特征，而是通过揭示塑造我们的迁徙和人口混合的历史。第二章“与尼安德特人的相遇”揭示了古代DNA的突破性技术如何提供了来自尼安德特人（我们大脑容量较大的近亲）的数据，并展示了他们如何与生活在非洲以外所有现代人类的祖先杂交。本章还解释了如何利用遗传数据来证明古代人群之间的混合确实发生过。第三章“古代DNA打开了潘多拉魔盒”重点介绍了古代DNA如何揭示出人们始料未及的过去特征，首先是丹尼索瓦人的发现。丹尼索瓦人是一个此前不为人知的古老族群。考古学家此前并未预料到，丹尼索瓦人的祖先与现代新几内亚人的祖先发生了混血。丹尼索瓦人基因组的测序引发了一系列关于其他古代人群及其混血情况的发现，并明确证明了人口混血是人类天性的核心特征。

Who We Are and How We Got Here is divided into three parts. Part I, “The Deep History of Our Species,” describes how the human genome not only provides all the information that a fertilized human egg needs to develop, but also contains within it the history of our species. Chapter 1, “How the Genome Explains Who We Are,” argues that the genome revolution has taught us about who we are as humans not by revealing the distinctive features of our biology compared to other animals but by uncovering the history of migrations and population mixtures that formed us. Chapter 2, “Encounters with Neanderthals,” reveals how the breakthrough technology of ancient DNA provided data from Neanderthals, our big-brained cousins, and showed how they interbred with the ancestors of all modern humans living outside of Africa. The chapter also explains how genetic data can be used to prove that ancient mixture between populations occurred. Chapter 3, “Ancient DNA Opens the Floodgates,” highlights how ancient DNA can reveal features of the past that no one had anticipated, starting with the discovery of the Denisovans, a previously unknown archaic population that had not been predicted by archaeologists and that mixed with the ancestors of present-day New Guineans. The sequencing of the Denisovan genome unleashed a cavalcade of discoveries of additional archaic populations and mixtures, and demonstrated unequivocally that population mixture is central to human nature.

第二部分“我们如何走到今天”讲述了基因组革命和古代DNA如何改变了我们对自身现代人类谱系的理解，并以人口混合为贯穿始终的主题，带领读者环游世界。第四章“人类的幽灵”提出了这样一个观点：我们可以根据现代人体内残留的遗传物质，重建那些已不复存在的单一族群。第五章“现代欧洲的形成”解释了现代欧洲人是由三个高度分化的族群融合而成，在过去的九千年里，这种融合方式是考古学家在古代DNA出现之前从未预料到的。第六章“塑造印度的碰撞”阐述了南亚人口的形成与欧洲人口的形成有何相似之处。在这两种情况下，九千年前来自近东的大规模农民迁徙与此前定居的狩猎采集者融合，随后五千年前来自欧亚草原的第二次大规模迁徙带来了不同的祖先构成，可能也带来了印欧语系。第七章“寻找美洲原住民祖先”展示了现代和古代DNA分析如何表明，欧洲人到来之前的美洲原住民的祖先来自多次来自亚洲的大规模迁徙。第八章“东亚人的基因组起源”描述了东亚人祖先的很大一部分源于中国农业中心地带人口的大规模扩张。第九章“将非洲重新纳入人类历史”重点阐述了古代DNA研究如何开始揭开非洲大陆深厚历史的面纱，揭示了近几千年来农民的大规模扩张如何淹没或与当地居民融合。

Part II, “How We Got to Where We Are Today,” is about how the genome revolution and ancient DNA have transformed our understanding of our own particular lineage of modern humans, and it takes readers on a tour around the world with population mixture as a unifying theme. Chapter 4, “Humanity’s Ghosts,” introduces the idea that we can reconstruct populations that no longer exist in unmixed form based on the bits of genetic material they have left behind in present-day people. Chapter 5, “The Making of Modern Europe,” explains how Europeans today descend from three highly divergent populations, which came together over the last nine thousand years in a way that archaeologists never anticipated before ancient DNA became available. Chapter 6, “The Collision That Formed India,” explains how the formation of South Asian populations parallels that of Europeans. In both cases, a mass migration of farmers from the Near East after nine thousand years ago mixed with previously established hunter-gatherers, and then a second mass migration from the Eurasian steppe after five thousand years ago brought a different kind of ancestry and probably Indo-European languages as well. Chapter 7, “In Search of Native American Ancestors,” shows how the analysis of modern and ancient DNA has demonstrated that Native American populations prior to the arrival of Europeans derive ancestry from multiple major pulses of migration from Asia. Chapter 8, “The Genomic Origins of East Asians,” describes how much of East Asian ancestry derives from major expansions of populations from the Chinese agricultural heartland. Chapter 9, “Rejoining Africa to the Human Story,” highlights how ancient DNA studies are beginning to peel back the veil on the deep history of the African continent drawn by the great expansions of farmers in the last few thousand years that overran or mixed with previously resident populations.

第三部分“颠覆性基因组”着重探讨基因组革命对社会的影响，并就我们如何理解自身在世界中的位置以及我们与世界的联系提出了一些建议。本书献给与我们共同生活在地球上的七十多亿人，以及生活在我们过去和未来的更多人口。第十章“不平等的基因组学”揭示了古代DNA研究如何基于社会权力不平等对生育成败的影响，揭示了不同人群、不同性别以及同一人群内部个体之间根深蒂固的不平等历史。第十一章“种族与身份的基因组学”指出，上个世纪以来形成的正统观念——即人类群体之间的亲缘关系过于密切，以至于他们之间不存在显著的平均生物学差异——已不再站得住脚，同时也表明，长期以来被视为替代方案的种族主义世界观与基因数据的启示更加格格不入。本章提出了一种理解人类群体间差异的新方法——一种基于基因组革命的方法。第十二章“古代DNA的未来”探讨了基因组革命的下一步发展方向。文章认为，借助古代DNA，基因组革命实现了卢卡·卡瓦利-斯福尔扎的梦想，成为研究古代人群的重要工具，其作用丝毫不逊于传统的考古学和历史语言学方法。古代DNA和基因组革命如今能够解答一个此前无法解答的关于遥远过去的难题：究竟发生了什么——古代人群彼此之间是如何联系的，以及迁徙如何促成了考古记录中显现的种种变化。古代DNA对考古学家而言无疑是一种解放，因为有了这些问题的答案，考古学家便可以着手研究他们一直以来至少同样感兴趣的课题：这些变化发生的原因。

Part III, “The Disruptive Genome,” focuses on the implications of the genome revolution for society. It offers some suggestions for how to conceive of our personal place in the world, our connection to the more than seven billion people who live on earth with us, and the even larger numbers of people who inhabit our past and future. Chapter 10, “The Genomics of Inequality,” shows how ancient DNA studies have revealed the deep history of inequality in social power among populations, between the sexes, and among individuals within a population, based on how that inequality determined success or failure of reproduction. Chapter 11, “The Genomics of Race and Identity,” argues that the orthodoxy that has emerged over the last century—the idea that human populations are all too closely related to each other for there to be substantial average biological differences among them—is no longer sustainable, while also showing that racist pictures of the world that have long been offered as alternatives are even more in conflict with the lessons of the genetic data. The chapter suggests a new way of conceiving the differences among human populations—a way informed by the genome revolution. Chapter 12, “The Future of Ancient DNA,” is a discussion of what comes next in the genome revolution. It argues that the genome revolution, with the help of ancient DNA, has realized Luca Cavalli-Sforza’s dream, emerging as a tool for investigating past populations that is no less useful than the traditional tools of archaeology and historical linguistics. Ancient DNA and the genome revolution can now answer a previously unresolvable question about the deep past: the question of what happened—how ancient peoples related to each other and how migrations contributed to the changes evident in the archaeological record. Ancient DNA should be liberating to archaeologists because with answers to these questions in reach, archaeologists can get on with investigating what they have always been at least as interested in, which is why the changes occurred.

在深入探讨这本书之前，我想先讲讲2009年我在麻省理工学院做客座讲座时发生的一件事。我的讲座是学期末的几场讲座之一，旨在为一门向学生介绍计算机辅助基因组研究的课程增添一些趣味性，这门课程的目标是找到疾病的治疗方法。当我讲到印度人口历史时，坐在前排中间的一位本科生直勾勾地盯着我。讲座结束后，她笑着问我：“你做这些研究的经费是怎么来的？”

Before diving into the book, I will recount something that happened during a guest lecture I gave at the Massachusetts Institute of Technology in 2009. Mine was one of the last lectures of the term, meant to add spice to a course aimed at introducing students to computer-aided research into genomes with the goal of finding cures for disease. As I addressed Indian population history, an undergraduate sitting at the center of the front row stared me down. When I concluded, she asked me, with a grin, “How do you get funded to do this stuff?”

我含糊其辞地提到，人类的过去如何塑造了基因变异，以及为了识别疾病的风险因素，了解过去至关重要。我举例说，在印度数千个不同的人群中，疾病发病率很高，这是因为创始人携带的突变随着人群的扩张而频率增加。我在向美国国立卫生研究院提交的申请中也提出了类似的论点，我计划寻找在不同人群中出现频率不同的疾病风险因素。自2003年我建立实验室以来，这类资助一直是我开展研究的主要资金来源。

I mumbled something about how the human past shapes genetic variation, and about how, in order to identify risk factors for disease, it is important to understand that past. I gave the example of how among the thousands of distinctive human populations of India, there are high rates of disease because mutations that happened to be carried by the founders increased in frequency as the groups expanded. I make arguments along these lines in my applications to the U.S. National Institutes of Health, in which I propose to find disease risk factors that occur at different frequencies across populations. Grants of this type have funded much of my work since I started my laboratory in 2003.

这些论点固然有道理，但我真希望当初能有不同的回应。我们科学家受制于科研经费体系，不得不从对健康或技术的实际应用角度来论证我们研究的合理性。但是，内在的好奇心难道不应该被珍视吗？对我们自身本质的根本探究，难道不应该成为我们人类作为一个物种所追求的巅峰吗？一个文明社会的标志之一，难道不正是重视那些可能不会立即产生经济或其他实际影响的智力活动吗？对人类过去——如同对艺术、音乐、文学或宇宙学的研究一样——至关重要，因为它让我们意识到我们共同境况中那些意义深远、且我们此前从未想象过的方面。

True as these arguments are, I wish I had responded differently. We scientists are conditioned by the system of research funding to justify what we do in terms of practical application to health or technology. But shouldn’t intrinsic curiosity be valued for itself? Shouldn’t fundamental inquiry into who we are be the pinnacle of what we as a species hope to achieve? Isn’t an attribute of an enlightened society that it values intellectual activity that may not have immediate economic or other practical impact? The study of the human past—as of art, music, literature, or cosmology—is vital because it makes us aware of aspects of our common condition that are profoundly important and that we heretofore never imagined.

第一部分

Part I

我们物种的深层历史

The Deep History of Our Species

1

1

 

 

基因组如何解释我们是谁

How the Genome Explains Who We Are

人类变异的编年史

The Master Chronicle of Human Variation

要理解遗传学为何能够揭示人类的过去，就必须了解基因组——即我们每个人从父母那里继承的全套遗传密码——是如何记录信息的。1953年，弗朗西斯·克里克、罗莎琳德·富兰克林、詹姆斯·沃森和莫里斯·威尔金斯证明，基因组是由大约30亿个化学构建单元（总共60亿个）组成的双链构成，这些构建单元可以被视为字母表中的字母：A（腺嘌呤）、C（胞嘧啶）、G（鸟嘌呤）和T（胸腺嘧啶）。^我们所说的“基因”是由这些链的微小片段组成，通常长度约为一千个碱基，它们作为模板来组装细胞中大部分功能的蛋白质。基因之间是非编码DNA，有时被称为“垃圾”DNA。可以通过对DNA片段进行化学反应的机器读取这些碱基的顺序，当反应沿着DNA序列进行时，机器会释放出闪光。对于字母 A、C、G 和 T，反应会发出不同的颜色，因此可以通过摄像头将字母序列扫描到计算机中。

To understand why genetics is able to shed light on the human past, it is necessary to understand how the genome—defined as the full set of genetic code each of us inherits from our parents—records information. Francis Crick, Rosalind Franklin, James Watson, and Maurice Wilkins showed in 1953 that the genome is written out in twin chains of about three billion chemical building blocks (six billion in all) that can be thought of as the letters of an alphabet: A (adenine), C (cytosine), G (guanine), and T (thymine).¹ What we call a “gene” consists of tiny fragments of these chains, typically around one thousand letters long, which are used as templates to assemble the proteins that do most of the work in cells. In between the genes is noncoding DNA, sometimes referred to as “junk” DNA. The order of the letters can be read by machines that perform chemical reactions on fragments of DNA, releasing flashes of light as the reactions pass along the length of the DNA sequence. The reactions emit a different color for each of the letters A, C, G, and T, so that the sequence of letters can be scanned into a computer by a camera.

尽管绝大多数科学家都专注于基因中包含的生物信息，但DNA序列之间也偶尔存在差异。这些差异是由于基因组复制过程中发生的随机错误（称为突变）造成的，这些错误发生在过去的某个时期。遗传学家正是通过研究这些差异来了解过去，这些差异大约每千个碱基对中就有一个，存在于基因和“垃圾”序列中。在约30亿个碱基对中，不相关的基因组之间通常存在约300万个差异。在任何片段上，两个基因组之间的差异密度越高，说明这两个片段距离它们拥有共同祖先的时间就越长，因为突变会随着时间的推移以大致恒定的速率积累。因此，差异密度就像一个生物学的秒表，记录着过去关键事件发生至今的时间。

Although the great majority of scientists are focused on the biological information that is contained within the genes, there are also occasional differences between DNA sequences. These differences are due to random errors in copying of genomes (known as mutations) that occurred at some point in the past. It is these differences, occurring about one every thousand letters or so in both genes and in “junk,” that geneticists study to learn about the past. Over the approximately three billion letters, there are typically around three million differences between unrelated genomes. The higher the density of differences separating two genomes on any segment, the longer it has been since the segments shared a common ancestor as the mutations accumulate at a more or less constant rate over time. So the density of differences provides a biological stopwatch, a record of how long it has been since key events occurred in the past.

遗传学在研究过去方面的第一个惊人应用涉及线粒体DNA。线粒体DNA是基因组中很小的一部分——大约只占基因组的二十万分之一——它通过母系遗传，从母亲传给女儿，再传给孙女。1987年，艾伦·威尔逊和他的同事对来自世界各地不同人群的几百个碱基对的线粒体DNA进行了测序。通过比较这些序列中不同的突变，他和同事们重建了一棵母系亲缘关系的家谱树。他们发现，这棵树最深的分支——最早从主干分出的分支——如今只存在于撒哈拉以南非洲血统的人群中，这表明现代人类的祖先生活在非洲。相比之下，所有非非洲裔人群都源自这棵树上较晚出现的分支。 ²这一发现成为20世纪80年代和90年代考古学、遗传学和骨骼证据综合分析的重要组成部分，该分析支持了现代人类起源于过去十万年左右生活在非洲的祖先的理论。根据已知的突变积累速率，威尔逊和他的同事估计，所有分支中最近的非洲祖先，即“线粒体夏娃”，生活在20万年前之后。³目前最佳的估计是大约16万年前，但需要注意的是，与大多数基因年代测定一样，由于人类基因突变发生的真实速率尚不确定，因此这个估计并不精确^。4

The first startling application of genetics to the study of the past involved mitochondrial DNA. This is a tiny portion of the genome—only approximately 1/200,000th of it—which is passed down along the maternal line from mother to daughter to granddaughter. In 1987, Allan Wilson and his colleagues sequenced a few hundred letters of mitochondrial DNA from diverse people around the world. By comparing the mutations that were different among these sequences, he and his colleagues were able to reconstruct a family tree of maternal relationships. What they found is that the deepest branch of the tree—the branch that left the main trunk earliest—is found today only in people of sub-Saharan African ancestry, suggesting that the ancestors of modern humans lived in Africa. In contrast, all non-Africans today descend from a later branch of the tree.² This finding became an important part of the triumphant synthesis of archaeological and genetic and skeletal evidence that emerged in the 1980s and 1990s for the theory that modern humans descend from ancestors who lived in the last hundred thousand years or so in Africa. Based on the rate at which mutations are known to accumulate, Wilson and his colleagues estimated that the most recent African ancestor of all the branches, “Mitochondrial Eve,” lived sometime after 200,000 years ago.³ The best current estimate is around 160,000 years ago, although it is important to realize that like most genetic dates, this one is imprecise because of uncertainty about the true rate at which human mutations occur.⁴

发现如此近期的共同祖先令人振奋，因为它驳斥了“多区域起源假说”。该假说认为，生活在非洲和欧亚大陆许多地区的现代人类主要起源于至少180万年前早期的一次迁徙（直立人）。直立人会制造粗糙的石器，脑容量约为现代人类的三分之二。多区域起源假说暗示，直立人的后代在非洲和欧亚大陆平行进化，最终形成了今天生活在同一地区的人群。因此，多区域起源假说预测，现代人类的线粒体DNA序列之间应该存在相隔近200万年的序列，而200万年正是直立人迁徙的年代。然而，遗传数据与这一预测无法吻合。事实上，所有现代人类都拥有一个共同的线粒体DNA祖先，其出现时间比直立人迁徙的时间晚了大约十倍，这表明现代人类主要起源于更晚时期从非洲的一次扩张。

The finding of such a recent common ancestor was exciting because it refuted the “multiregional hypothesis,” according to which present-day humans living in many parts of Africa and Eurasia descend substantially from an early dispersal (at least 1.8 million years ago) of Homo erectus, a species that made crude stone tools and had a brain about two-thirds the size of ours. The multiregional hypothesis implied that descendants of Homo erectus evolved in parallel across Africa and Eurasia to give rise to the populations that live in the same places today. The multiregional hypothesis would therefore predict that there would be mitochondrial DNA sequences among present-day people that are separated by close to two million years, the age of the dispersal of Homo erectus. However, the genetic data was impossible to reconcile with this prediction. The fact that all people today share a common mitochondrial DNA ancestor about ten times more recently showed that humans today largely descend from a much later expansion from Africa.

人类学证据指向了一种可能的情况。最早的人类骨骼具有“解剖学意义上的现代”特征——定义为在球形脑壳和其他方面符合当今所有人类变异范围——这些特征可以追溯到20万至30万年前，而且全部来自非洲。 ⁵ 然而，在非洲和近东以外，尚无确凿证据表明解剖学意义上的现代人类生活在10万年前，而5万年前的证据也十分有限。 ⁶石器类型的考古证据也表明，大约5万年前发生了巨大的变化，西欧亚大陆的考古学家将这一时期称为旧石器时代晚期，而非洲的考古学家则称之为晚期石器时代。此后，石器制造技术发生了显著变化，其风格每隔几千年就会发生变化，这与之前缓慢的变化速度截然不同。这一时期的人类也开始留下更多展现其审美和精神生活的器物：鸵鸟蛋壳制成的珠子、抛光的石手镯、用红色氧化铁制成的人体彩绘，以及世界上最早的具象艺术。世界上已知最早的雕像是一件约有四万年历史的“狮人”，由猛犸象牙雕刻而成，发现于德国霍伦斯坦-施塔德尔。7 法国肖维岩洞岩壁上发现的约有三万年历史的冰河时代前动物壁画，即使在今天也依然是超凡脱俗^的艺术杰作。

Anthropological evidence pointed to a likely scenario for what occurred. The earliest human skeletons with “anatomically modern” features—defined as falling within the range of variation of all humans today with regard to having a globular brain case and other traits—date up to two hundred to three hundred thousand years ago and are all from Africa.⁵ Outside of Africa and the Near East, though, there is no convincing evidence of anatomically modern humans older than a hundred thousand years and very limited evidence older than around fifty thousand years.⁶ Archaeological evidence of stone tool types also points to a great change after around fifty thousand years ago, a period known to archaeologists of West Eurasia as the Upper Paleolithic, and to archaeologists of Africa as the Later Stone Age. After this time, the technology for manufacturing stone tools became very different, and there were changes in style every few thousand years, compared to the glacial earlier pace of change. Humans in this period also began to leave behind far more artifacts that revealed their aesthetic and spiritual lives: beads made of ostrich eggshells, polished stone bracelets, body paint made from red iron oxide, and the world’s first representational art. The world’s earliest known figurine is a roughly forty-thousand-year-old “lion-man” carved from a woolly mammoth tusk, found in Hohlenstein-Stadel in Germany.⁷ The approximately thirty-thousand-year-old drawings of pre–ice age beasts, found on the walls of Chauvet Cave in France, even today are recognizable as transcendent art.

大约五万年前之后，考古记录中的变化急剧加速，这也反映在人口变化的证据中。尼安德特人大约在四十万年前在欧洲进化，由于他们的骨骼形态不符合现代人类的变异范围，因此被认为是“古老”的。大约在四万一千年到三万九千年之间，他们在西欧最后的据点灭绝，距离现代人类的到来仅几千年之遥。8^人口更替也发生在欧亚大陆的其他地区以及南部非洲，那里有遗址被废弃和晚期石器时代文化突然出现的证据^。9

The dramatic acceleration of change in the archaeological record after around fifty thousand years ago was also reflected by evidence of population change. The Neanderthals, who had evolved in Europe by around four hundred thousand years ago and are considered “archaic” in the sense that their skeletal shape did not fall within present-day human variation, went extinct in their last holdout of western Europe between about forty-one thousand and thirty-nine thousand years ago, within a few thousand years of the arrival of modern humans.⁸ Population turnovers also occurred elsewhere in Eurasia, as well as in southern Africa, where there is evidence of abandonment of sites and the sudden appearance of Later Stone Age cultures.⁹

所有这些变化的自然解释是解剖学意义上的现代人类群体的传播，他们的祖先包括“线粒体夏娃”，他们实践了一种复杂的新文化，并且在很大程度上取代了之前居住在各个地方的人们。

The natural explanation for all these changes was the spread of an anatomically modern human population whose ancestors included “Mitochondrial Eve,” who practiced a sophisticated new culture, and who largely replaced the people who lived in each place before.

基因开关的诱惑

The Siren Call of the Genetic Switch

20世纪80年代和90年代，遗传学能够帮助区分关于人类起源的各种假说，这一发现曾使人们对这门学科提供简明解释的能力感到无比兴奋。一些人甚至开始思考，遗传学是否不仅能为现代人类大约五万年前从非洲和近东扩散提供佐证，还能发挥更大的作用。或许基因本身就是人类扩散的原因，它能像DNA中那四字母代码一样，为考古记录中人类进化速度的加快提供简洁而精妙的解释。

The finding that genetics could help to distinguish between competing hypotheses of human origins led in the 1980s and 1990s to exuberance about the power of the discipline to provide simple explanations. Some even wondered if genetics might be able to do more than provide a supporting line of evidence for the spread of modern humans from Africa and the Near East after around fifty thousand years ago. Perhaps genes could also be the cause of that spread, offering an explanation as simple and beautiful as the four-letter code written in DNA for the quickening pace of change in the archaeological record.

因提出基因改变或许可以解释我们与祖先行为差异的理论而闻名的人类学家是理查德·克莱因。他提出，大约五万年前，非洲晚期石器时代革命和西欧亚大陆旧石器时代晚期革命——现代人类行为的显著发展时期——是由影响大脑生物学的单一基因突变频率的增加所驱动的，这种突变使得制造创新工具和发展复杂行为成为可能。

The anthropologist best known for embracing the idea that a genetic change might explain how we came to be behaviorally distinct from our predecessors was Richard Klein. He put forward the idea that the Later Stone Age revolution of Africa and the Upper Paleolithic revolution of western Eurasia, when recognizably modern human behavior burst into full flower after about fifty thousand years ago, were driven by the rise in frequency of a single mutation of a gene affecting the biology of the brain, which permitted the manufacture of innovative tools and the development of complex behavior.

根据克莱因的理论，这种突变频率的增加使人类具备了某些关键特征，例如使用概念性语言的能力。克莱因认为，在这种突变发生之前，人类不具备现代行为能力。其他物种中少数基因变化就能带来重大适应的例子也支持了他的观点，例如，墨西哥野生草类类蜀黍的小穗只需五种基因变化就能变成我们今天在超市里买到的大玉米棒。 ¹⁰

According to Klein’s theory, the rise in frequency of this mutation primed humans for some enabling trait, such as the ability to use conceptual language. Klein thought that prior to the occurrence of this mutation, humans were incapable of modern behaviors. Supporting his notion are examples among other species of a small number of genetic changes that have effected major adaptations, such as the five changes that are sufficient to turn the tiny ears of the Mexican wild grass teosinte into the huge cobs of corn that we buy in the supermarket today.¹⁰

克莱因的假说几乎在他提出之初就遭到了猛烈的批评，其中最引人注目的是考古学家萨莉·麦克布雷蒂和艾莉森·布鲁克斯的批评。她们指出，克莱因认为的几乎所有现代人类的显著特征都与现代人类相悖。在非洲和近东的考古记录中，早在旧石器时代晚期和新石器时代过渡之前的数万年，就已出现了人类行为。 ¹¹但即便没有哪一种行为是全新的，克莱因也指出了某些重要的东西。五万年前之后，现代人类行为的证据显著增强，这是不容否认的，这也引发了一个问题：生物变化是否对此有所贡献？

Klein’s hypothesis came under intense criticism almost as soon as he suggested it, most notably from the archaeologists Sally McBrearty and Alison Brooks, who showed that almost every trait that Klein considered to be a hallmark of distinctly modern human behavior was evident in the African and Near Eastern archaeological records tens of thousands of years before the Upper Paleolithic and Later Stone Age transitions.¹¹ But even if no single behavior was new, Klein had put his finger on something important. The intensification of evidence for modern human behavior after fifty thousand years ago is undeniable, and raises the question of whether biological change contributed to it.

在遗传学被认为能够为重大谜团提供简单解释的时代，一位名叫斯万特·帕博（Svante Pääbo）的遗传学家崭露头角。他于“线粒体夏娃”发现后不久加入艾伦·威尔逊（Allan Wilson）的实验室，并参与发明了古代DNA革命的大部分工具，还完成了尼安德特人基因组的测序。2002年，帕博和他的同事发现了FOXP2基因中的两个突变，这两个突变似乎是大约五万年前之后发生巨大变化的候选突变。此前一年，医学遗传学家已经确定FOXP2基因发生突变会导致一种罕见的综合征，患者虽然认知能力正常，但却无法使用复杂的语言，包括大部分语法。^帕博和他的同事证明， FOXP2基因产生的蛋白质在黑猩猩和老鼠之间超过一亿年的进化过程中几乎保持不变。然而，自人类从与黑猩猩的共同祖先群体中分化出来以来，仅在人类谱系中发生了两次蛋白质变化，这表明该基因在人类谱系上的进化速度要快得多。 ¹³帕博及其同事后来的研究发现，携带人类FOXP2基因的基因工程小鼠在大多数方面与普通小鼠相同，但发出吱吱声的方式不同，这与这些变化影响声音形成的观点相符。 ¹⁴由于尼安德特人也携带这两种FOXP2基因突变， ¹⁵但它们不可能在五万年前之后对FOXP2基因的变化产生影响。然而，帕博及其同事后来发现了一种几乎存在于所有现代人类中的第三种突变，这种突变会影响FOXP2何时以及在哪些细胞中转化为蛋白质。尼安德特人没有这种变化，因此，这种突变可能是现代人类在数十万年前与尼安德特人分离后进化过程中起作用的候选突变。 ¹⁶

One geneticist who came of age at this time of exuberance about the power of genetics to provide simple explanations for great mysteries was Svante Pääbo, who arrived in Allan Wilson’s laboratory just after the “Mitochondrial Eve” discovery, and who would go on to invent much of the toolkit of the ancient DNA revolution and to sequence the Neanderthal genome. In 2002, Pääbo and his colleagues discovered two mutations in the gene FOXP2 that seemed to be candidates for propelling the great changes that occurred after around fifty thousand years ago. The previous year, medical geneticists had identified FOXP2 as a gene that, when mutated, produces an extraordinary syndrome whose sufferers have normal-range cognitive capabilities, but cannot use complex language, including most grammar.¹² Pääbo and his colleagues showed that the protein produced by the FOXP2 gene has remained almost identical during the more than hundred million years of evolution separating chimpanzees and mice. However, two changes to the protein occurred on just the human lineage since it branched out of the common ancestral population of humans and chimpanzees, showing that the gene had evolved much more rapidly on the human lineage.¹³ Later work by Pääbo and his colleagues found that engineered mice with the human versions of FOXP2 are identical to regular mice in most respects, but squeak differently, consistent with the idea that these changes affect the formation of sounds.¹⁴ These two mutations at FOXP2 cannot have contributed to the changes after fifty thousand years ago, since Neanderthals shared them,¹⁵ but Pääbo and his colleagues later identified a third mutation that is found in almost all present-day humans and that affects when and in what cells FOXP2 gets turned into protein. This change is absent in Neanderthals, and thus is a candidate for contributing to the evolution of modern humans after their separation from Neanderthals hundreds of thousands of years ago.¹⁶

无论FOXP2本身在现代人类生物学中的重要性如何，帕博（Pääbo）都将探寻现代人类行为的遗传基础作为对古人类基因组进行测序的理由。 ¹⁷在2010年至2013年间，帕博领导了一系列研究，发表了包括尼安德特人在内的古人类的全基因组序列。他的论文重点阐述了一个不断更新的列表，该列表包含约十万个基因组位点，几乎所有现代人类都携带着尼安德特人所没有的基因改变。 ¹⁸这份列表中肯定隐藏着一些具有重要生物学意义的改变，但我们目前仍处于确定这些改变的初期阶段，这反映出一个更普遍的问题：我们在解读基因组方面就像幼儿园小朋友一样。虽然我们已经学会了解码单个“单词”（例如，我们知道DNA碱基序列如何转化为蛋白质），但我们仍然无法理解整个基因组的运作机制。

Regardless of how important FOXP2 itself is in modern human biology, Pääbo cites the search for the genetic basis for modern human behavior as a justification for sequencing the genomes of archaic humans.¹⁷ Between 2010 and 2013, when he led a series of studies that published whole-genome sequences from archaic humans like Neanderthals, Pääbo’s papers highlighted an evolving list of about one hundred thousand places in the genome where nearly all present-day humans carry genetic changes that are absent in Neanderthals.¹⁸ There are surely biologically important changes hiding in the list, but we are still only at the very beginning of the process of determining what they are, reflecting a more general problem that we are like kindergartners in our ability to read the genome. While we have learned to decode the individual words—as we know how the sequence of DNA letters gets turned into proteins—we still can’t parse the sentences.

令人遗憾的是，像FOXP2这样在自然选择的压力下，人类祖先基因突变频率增加，且我们对其功能有所了解的例子屈指可数。在这些例子中，我们只能依靠研究生或博士后科学家多年来与生命奥秘的艰苦斗争，通过基因工程改造小鼠或鱼类，才能获得这些见解。这表明，我们需要开展一项进化论版的“曼哈顿计划”，才能理解我们拥有而尼安德特人所没有的每一个突变的功能。这项人类进化生物学的“曼哈顿计划”值得我们全人类共同参与。但即便最终得以实施，我预计研究结果也会极其复杂——因为人类的独特性是由众多个体基因变化共同作用的结果——以至于很少有人能够理解。尽管科学问题至关重要，但我预计，我们永远无法找到既符合逻辑又令人信服的分子层面的现代行为解释。

The sad truth is that it is possible to count on the fingers of two hands the examples like FOXP2 of mutations that increased in frequency in human ancestors under the pressure of natural selection and whose functions we partly understand. In each of these cases, the insights only came from years of hand-to-hand combat with life’s secrets by graduate students or postdoctoral scientists making engineered mice or fish, suggesting that it will take an evolutionary Manhattan Project to understand the function of each mutation that we have and that Neanderthals do not. This Manhattan Project of human evolutionary biology is one to which we as a species should commit ourselves. But even when it is carried out, I expect that the findings will be so complicated—with so many individual genetic changes contributing to what makes humans distinctive—that few people will find the answer comprehensible. While the scientific question is profoundly important, I expect that no intellectually elegant and emotionally satisfying molecular explanation for behavioral modernity will ever be found.

但即便仅仅研究基因组中的几个位点无法对现代人类行为的演化提供令人满意的解释，基因组革命最大的惊喜在于它正从另一个视角——历史视角——开始提供解释。通过理解整个基因组，超越线粒体DNA和Y染色体所揭示的过往历史的一小部分，我们或许能够更好地理解人类行为的演化。通过染色体，并拥抱我们祖先众多足迹所谱写的过往故事（这些故事记录在我们整个基因组的档案中），我们已经开始勾勒出一幅关于我们如何成为如今这般模样的全新图景。本书的主题正是基于这种基于迁徙和人口混合的解释。

But even if studying just a few locations in the genome will not provide a satisfying explanation for how modern human behavior evolved, the great surprise of the genome revolution is the explanations it is starting to provide from another perspective—that of history. By comprehending the entire genome—by going beyond the tiny slice of the past sampled by our mitochondrial DNA and Y chromosome and embracing the story of our past told by the multiplicity of our ancestors that is written in the record of our whole genome—we have already begun to sketch out a new picture of how we got to be the way we are. This explanation based on migrations and population mixture is the subject of this book.

十万个亚当和夏娃

One Hundred Thousand Adams and Eves

1987年，记者罗杰·莱文（Roger Lewin）将当今所有人的共同母系祖先称为“线粒体夏娃”，这让人联想到一个创世故事——一位女性是所有人的母亲，她的后代遍布世界各地。 ¹⁹ 这个名称激发了人们的集体想象，至今不仅被公众使用，也被许多科学家用来指代这位共同的母系祖先。然而，这个名称带来的误导远大于益处。它助长了一种错误的印象，即我们所有人的DNA都来自两位祖先，而要了解我们的历史，只需追踪由线粒体DNA代表的纯母系血统和由Y染色体代表的纯父系血统即可。受此启发，美国国家地理学会于2005年启动了“基因组计划”，收集了近百万不同族裔人群的线粒体DNA和Y染色体数据。但这个项目在启动之前就已经过时了。它主要是一种娱乐活动，几乎没有产生任何有意义的科学成果。从一开始就很明显，线粒体DNA和Y染色体数据中关于人类历史的大部分信息已经被挖掘殆尽，而更丰富的故事则隐藏在整个基因组中。

When the journalist Roger Lewin in 1987 dubbed the common maternal ancestor of all people living today “Mitochondrial Eve,” he evoked a creation story—that of a woman who was the mother of us all, and whose descendants dispersed throughout the earth.¹⁹ The name captured the collective imagination, and is still used not only by the public but also by many scientists to refer to this common maternal ancestor. But the name has been more misleading than helpful. It has fostered the mistaken impression that all of our DNA comes from precisely two ancestors and that to learn about our history it would be sufficient to simply track the purely maternal line represented by mitochondrial DNA, and the purely paternal line represented by the Y chromosome. Inspired by this possibility, the National Geographic Society’s “Genographic Project,” beginning in 2005, collected mitochondrial DNA and Y-chromosome data from close to a million people of diverse ethnic groups. But the project was outdated even before it began. It has been largely recreational, and has produced few interesting scientific results. From the outset, it was clear that most of the information about the human past present in mitochondrial DNA and Y-chromosome data had already been mined, and that far richer stories were buried in the whole genome.

事实上，基因组包含了众多不同祖先的故事——数万个独立的谱系，而不仅仅是可以通过Y染色体和线粒体DNA追溯的那两个谱系。要理解这一点，我们需要认识到，除了线粒体DNA之外，基因组并非来自单一祖先的连续序列，而是一个镶嵌体。这46个镶嵌体单元，或者说，是染色体——长长的……细胞内物理上分离的DNA。一个基因组由23条染色体组成，由于一个人携带两个基因组，分别来自父母双方，因此染色体总数为46条。

The truth is that the genome contains the stories of many diverse ancestors—tens of thousands of independent genealogical lineages, not just the two whose stories can be traced with the Y chromosome and mitochondrial DNA. To understand this, one needs to realize that beyond mitochondrial DNA, the genome is not one continuous sequence from a single ancestor but is instead a mosaic. Forty-six of the mosaic tiles, as it were, are chromosomes—long stretches of DNA that are physically separated in the cell. A genome consists of twenty-three chromosomes, and because a person carries two genomes, one from each parent, the total number is forty-six.

但染色体本身是由更小的片段拼接而成的。例如，女性传递给卵子的染色体前三分之一可能来自父亲，后三分之二来自母亲，这是由于其卵巢中父母双方的该染色体拷贝拼接而成。女性在产生卵子时平均会产生约45个新的拼接片段，而男性在产生精子时会产生约26个拼接片段，因此每一代总共会产生约71个新的拼接片段。 ²⁰ 因此，当我们追溯每一代的祖先时，一个人的基因组是由越来越多的祖先片段拼接而成的。

But the chromosomes themselves are mosaics of even smaller tiles. For example, the first third of a chromosome a woman passes down to her egg might come from her father and the last two-thirds from her mother, the result of a splicing together of her father’s and mother’s copies of that chromosome in her ovaries. Females create an average of about forty-five new splices when producing eggs, while males create about twenty-six splices when producing sperm, for a total of about seventy-one new splices per generation.²⁰ So it is that as we trace each generation back further into the past, a person’s genome is derived from an ever-increasing number of spliced-together ancestral fragments.

这意味着我们的基因组中包含着众多祖先的基因。每个人的基因组都源自47个DNA片段，分别对应于父母遗传的染色体以及线粒体DNA。追溯上一代，一个人的基因组源自大约118个（47+71）DNA片段，这些片段由父母遗传。再往前追溯两代，祖先DNA片段的数量增加到大约189个（47+71+另外71），这些片段由四位祖父母遗传。如果再往前追溯更久远，祖先DNA片段数量的增长速度很快就会被祖先数量的倍增所超越。例如，追溯到十代，祖先DNA片段的数量约为757个，但祖先的数量却高达1024个，这意味着每个人都有数百位祖先，而我们并没有从他们那里获得任何DNA。二十代以前，祖先的数量几乎是个人基因组中祖先 DNA 片段数量的一千倍，因此可以肯定的是，每个人都没有从其绝大多数实际祖先那里继承任何 DNA。

This means that our genomes hold within them a multitude of ancestors. Any person’s genome is derived from 47 stretches of DNA corresponding to the chromosomes transmitted by mother and father plus mitochondrial DNA. One generation back, a person’s genome is derived from about 118 (47 plus 71) stretches of DNA transmitted by his or her parents. Two generations back, the number of ancestral stretches of DNA grows to around 189 (47 plus 71 plus another 71) transmitted by four grandparents. Look even further back in time, and the additional increase in ancestral stretches of DNA every generation is rapidly overtaken by the doubling of ancestors. Ten generations back, for example, the number of ancestral stretches of DNA is around 757 but the number of ancestors is 1,024, guaranteeing that each person has several hundred ancestors from whom he or she has received no DNA whatsoever. Twenty generations in the past, the number of ancestors is almost a thousand times greater than the number of ancestral stretches of DNA in a person’s genome, so it is a certainty that each person has not inherited any DNA from the great majority of his or her actual ancestors.

这些计算表明，根据历史记录重建的一个人的家谱与其遗传基因并不相同。《圣经》和王室编年史记载了数十代人的血缘关系。然而，即使家谱准确无误，英国女王伊丽莎白二世的血统也几乎肯定与此无关。伊丽莎白二世女王并未从征服英格兰的诺曼底公爵威廉那里继承任何DNA。威廉被认为是她二十四代之前的祖先。²¹这并不意味着伊丽莎白二世女王没有从那么久远的祖先那里继承DNA，只是说在她16,777,216位二十四代祖先中，预计只有大约1,751位为她贡献了DNA。这个比例如此之小，以至于威廉成为她基因祖先的唯一合理解释是，他是她二十四代之前的世系祖先。数千条不同的血统路线，即使考虑到英国王室近亲繁殖程度很高，这似乎也不太可能。

These calculations mean that a person’s genealogy, as reconstructed from historical records, is not the same as his or her genetic inheritance. The Bible and the chronicles of royal families record who begat whom over dozens of generations. Yet even if the genealogies are accurate, Queen Elizabeth II of England almost certainly inherited no DNA from William of Normandy, who conquered England in 1066 and who is believed to be her ancestor twenty-four generations back in time.²¹ This does not mean that Queen Elizabeth II did not inherit DNA from ancestors that far back, just that it is expected that only about 1,751 of her 16,777,216 twenty-fourth-degree genealogical ancestors contributed any DNA to her. This is such a small fraction that the only way William could plausibly be her genetic ancestor is if he was her genealogical ancestor in thousands of different lineage paths, which seems unlikely even considering the high level of inbreeding in the British royal family.

随着时间推移，一个人的基因组会分散到越来越多的祖先DNA片段中，这些片段分布在数量庞大的祖先身上。追溯到五万年前，我们的基因组会分散到超过十万个祖先DNA片段中，这比当时任何族群的人口数量都要多。因此，我们几乎继承了所有在遥远过去拥有大量后代的祖先的DNA。

Going back deeper in time, a person’s genome gets scattered into more and more ancestral stretches of DNA spread over ever-larger numbers of ancestors. Tracing back fifty thousand years in the past, our genome is scattered into more than one hundred thousand ancestral stretches of DNA, greater than the number of people who lived in any population at that time, so we inherit DNA from nearly everyone in our ancestral population who had a substantial number of offspring at times that remote in the past.

然而，基因组序列比对所能提供的关于远古时间的信息是有限的。在基因组的每个位置，如果我们追溯足够久远的祖先，就会到达一个共同祖先的起点，超过这个起点，我们就无法通过比较现代人的DNA序列来获取任何关于更远时间的信息。从这个角度来看，基因组中每个位置的共同祖先就像天体物理学中的一个黑洞，任何关于更远时间的信息都无法从中逃逸。对于线粒体DNA而言，这个黑洞出现在大约16万年前，即“线粒体夏娃”时期。对于基因组其余大部分区域而言，这个黑洞出现在500万至100万年前，因此基因组的其余部分可以提供比线粒体DNA分析所能获取的更远时间的信息。22^再往后，一切都将陷入黑暗。

There is a limit, though, to the information that comparison of genome sequences provides about deep time. At each place in the genome, if we trace back our lineages far enough into the past, we reach a point where everyone descends from the same ancestor, beyond which it becomes impossible to obtain any information about deeper time from comparison of the DNA sequences of people living today. From this perspective, the common ancestor at each point in the genome is like a black hole in astrophysics, from which no information about deeper time can escape. For mitochondrial DNA this black hole occurs around 160,000 years ago, the date of “Mitochondrial Eve.” For the great majority of the rest of the genome the black hole occurs between five million and one million years ago, and thus the rest of the genome can provide information about far deeper time than is accessible through analysis of mitochondrial DNA.²² Beyond this, everything goes dark.

追溯如此众多的血统，揭示过去的力量是非凡的。在我看来，当我想到基因组时，我并不把它看作是当下的产物，而是深深扎根于时间之中，如同织锦般由世系和DNA序列交织而成，从父母传给子女，蜿蜒回溯到遥远的过去。追溯过去，这些线索穿过越来越多的祖先，提供每一代人口规模和亚结构的信息。例如，当说一位非裔美国人拥有80%的西非血统和20%的欧洲血统时，这意味着大约五百年前，在欧洲殖民主义引发的人口迁徙和融合之前，这个人80%的祖先血统都来自欧洲。一部分人可能居住在西非，其余的人可能居住在欧洲。但这种说法就像电影中的静止画面，只捕捉了过去的一个瞬间。同样合理的观点是，十万年前，绝大多数非裔美国人的祖先，就像今天所有人的祖先一样，都生活在非洲。

The power of tracing this multitude of lineages to reveal the past is extraordinary. In my mind’s eye, when I think of a genome, I view it not as a thing of the present, but as deeply rooted in time, a tapestry of threads consisting of lines of descent and DNA sequences copied from parent to child winding back into the distant past. Tracing back, the threads wind themselves through ever more ancestors, providing information about population size and substructure in each generation. When an African American person is said to have 80 percent West African and 20 percent European ancestry, for example, a statement is being made that about five hundred years ago, prior to the population migrations and mixtures precipitated by European colonialism, 80 percent of the person’s ancestral threads probably resided in West Africa and the remainder probably lived in Europe. But such statements are like still frames in a movie, capturing one point in the past. An equally valid perspective is that one hundred thousand years ago, the vast majority of lineages of African American ancestors, like those of everyone today, were in Africa.

我们基因组中无数个体讲述的故事

The Story Told by the Multitudes in Our Genomes

2001年，人类基因组首次被测序——这意味着绝大多数的DNA化学碱基已被读取。约70%的序列来自一位非裔美国人，^23岁，但也有部分来自其他人。到2006年，一些公司开始销售机器人，将DNA碱基读取的成本降低了一万倍以上，很快又降低了十万倍，使得绘制更多人的基因组图谱变得经济实惠。因此，人们不仅可以比较来自少数孤立区域（例如线粒体DNA）的序列，还可以比较来自整个基因组的序列。这使得重建每个人数万条祖先谱系​​成为可能。这彻底改变了对过去历史的研究。科学家们可以收集数量级更大的数据，并检验由整个基因组揭示的人类物种历史是否与由线粒体DNA和Y染色体揭示的历史一致。

In 2001, the human genome was sequenced for the first time—which means that the great majority of its chemical letters were read. About 70 percent of the sequence came from a single individual, an African American,²³ but some came from other people. By 2006, companies began selling robots that reduced the cost of reading DNA letters by more than ten thousandfold and soon by one hundred thousandfold, making it economical to map the genomes of many more people. It thus became possible to compare sequences not just from a few isolated locations, such as mitochondrial DNA, but from the whole genome. That made it possible to reconstruct each person’s tens of thousands of ancestral lines of descent. This revolutionized the study of the past. Scientists could gather orders of magnitude more data, and test whether the history of our species suggested by the whole genome was the same as that told by mitochondrial DNA and the Y chromosome.

2011年，李恒和理查德·德宾发表的一篇论文表明，一个人的基因组包含众多祖先信息的想法并非仅仅是一种理论上的可能性，而是现实。为了从一个人的DNA中解读一个群体的深层历史，李恒和德宾利用了这样一个事实：每个人实际上都携带两个基因组——一个来自父亲，一个来自母亲。 ²⁴因此，可以通过计算一个人从母亲那里继承的基因组和从父亲那里继承的基因组之间的突变数量，来确定他们在每个地点拥有共同祖先的时间。通过考察这些祖先生活的年代范围——绘制十万个亚当和……的年龄图——伊夫斯-李和德宾分别在不同时期确定了祖先群体的规模。在小群体中，两个随机选择的基因组序列很可能源自同一个亲本基因组序列，因为携带它们的个体拥有共同的祖先。然而，在大群体中，这种概率要低得多。因此，过去人口规模较小的时期，可以通过历史上那些谱系中不成比例地存在共同祖先证据的时期来确定。沃尔特·惠特曼在诗歌《自我之歌》中写道：“我自相矛盾吗？/很好，那我就是自相矛盾，/（我庞大，我包含无数）”惠特曼的话也完全可以用来形容李和德宾的实验，该实验证明，整个群体的历史都包含在一个人的基因组中，因为该人的基因组记录了众多祖先的历史。

A 2011 paper by Heng Li and Richard Durbin showed that the idea that a single person’s genome contains information about a multitude of ancestors was not just a theoretical possibility, but a reality. To decipher the deep history of a population from a single person’s DNA, Li and Durbin leveraged the fact that any single person actually carries not one but two genomes: one from his or her father and one from his or her mother.²⁴ Thus it is possible to count the number of mutations separating the genome a person receives from his or her mother and the genome the person receives from his or her father to determine when they shared a common ancestor at each location. By examining the range of dates when these ancestors lived—plotting the ages of one hundred thousand Adams and Eves—Li and Durbin established the size of the ancestral population at different times. In a small population, there is a substantial chance that two randomly chosen genome sequences derive from the same parent genome sequence, because the individuals who carry them share a parent. However, in a large population the chance is far lower. Thus, the times in the past when the population size was low can be identified based on the periods in the past when a disproportionate fraction of lineages have evidence of sharing common ancestors. Walt Whitman, in the poem “Song of Myself,” wrote, “Do I contradict myself? / Very well, then I contradict myself, / (I am large, I contain multitudes).” Whitman could just as well have been talking about the Li and Durbin experiment and its demonstration that a whole population history is contained within a single person as revealed by the multitude of ancestors whose histories are recorded within that person’s genome.

李和德宾的研究一项出人意料的发现是，在非非洲人群和非洲人群分离之后，非非洲人群的共同历史中存在一段较长的时期，在此期间人口规模较小，这体现在跨越数万年的众多共同祖先的证据上。 ²⁵非非洲人群中存在共同的“瓶颈事件”（即少数祖先繁衍出如今大量的后代）并非新发现。但在李和德宾的研究之前，人们对这一事件的持续时间知之甚少，而且似乎有可能它只持续了几代人的时间——例如，一小群人穿越撒哈拉沙漠进入北非，或者从非洲迁徙到亚洲。李和德宾的研究也难以解释人口规模长期较小的现象，这与大约五万年前现代人类在非洲内外持续扩张的观点相吻合。我们的历史可能并不像一个强大的群体所到之处都能立即取得成功的故事那么简单。

An unanticipated finding of the Li and Durbin study was its evidence that after the separation of non-African and African populations, there was an extended period in the shared history of non-Africans when populations were small, as reflected in evidence for many shared ancestors spread over tens of thousands of years.²⁵ A shared “bottleneck event” among non-Africans—when a small number of ancestors gave rise to a large number of descendants today—was not a new finding. But prior to Li and Durbin’s work, there was no good information about the duration of this event, and it seemed plausible that it could have transpired over just a few generations—for example, a small band of people crossing the Sahara into North Africa, or from Africa into Asia. The Li and Durbin evidence of an extended period of small population size was also hard to square with the idea of an unstoppable expansion of modern humans both within and outside Africa around fifty thousand years ago. Our history may not be as simple as the story of a dominant group that was immediately successful wherever it went.

全基因组视角如何

终结简单的解释

How the Whole-Genome Perspective

Put an End to Simple Explanations

近几十年来技术的飞速发展，使得我们能够以全基因组视角研究人类生物学，从而以前所未有的精细程度重建人口历史。由此揭示，以往仅基于线粒体DNA构建的简单图景，以及关于一两个基因变化推动了旧石器时代晚期和旧石器时代晚期过渡的简单解释——即现代人类行为在非洲和欧亚大陆的考古遗址中广泛传播——已不再成立。

The newfound ability to take a whole-genome view of human biology, made possible by leaps in technology in the last decades, has allowed reconstruction of population history in far more detail than had been previously possible. In doing so it revealed that the simple picture from mitochondrial DNA, and the just-so stories about one or a few changes propelling the Later Stone Age and Upper Paleolithic transitions when recognizably modern human behavior became widespread as reflected in archaeological sites across Africa and Eurasia, are no longer tenable.

2016年，我和我的同事们采用了李和杜宾方法 ²⁶的改进版，将世界各地的人群与最早分化的现代人类谱系进行比较。该谱系为当今人类群体贡献了大部分祖先：即为南部非洲桑人狩猎采集者贡献了绝大部分祖先的谱系。我们的研究 ²⁷ 与大多数其他研究 ²⁸一样发现，这种分化大约始于20万年前，并在10万多年前基本完成。证据是，桑人基因组与非桑人基因组之间突变的密度普遍很高，这意味着在过去的10万年中，桑人和非桑人之间共同的祖先很少。来自中非森林的“俾格米人”群体也拥有同样独特的祖先。某些人类群体之间极其古老的隔离与这样一种观点相矛盾：即对现代人类独特行为至关重要的单一突变发生在旧石器时代晚期和新石器时代晚期之前不久。在现代人类行为发展到这一时期后，一项关键的改变理应在某些人群中频繁出现——即那些源自突变发生人群的后代——而在其他人群中则可能缺失或极为罕见。然而，这似乎难以解释为何如今所有人都能掌握概念性语言，并以现代人类特有的方式革新自身文化。

In 2016, my colleagues and I used an adaptation of the Li and Durbin method²⁶ to compare populations from around the world to the earliest branching modern human lineage that has contributed a large proportion of the ancestry of a population living today: the one that contributed the lion’s share of ancestry to the San hunter-gatherers of southern Africa. Our study,²⁷ like most others,²⁸ found that the separation had begun by around two hundred thousand years ago and was mostly complete by more than one hundred thousand years ago. The evidence for this is that the density of mutations separating San genomes from non-San genomes is uniformly high, implying few shared ancestors between San and non-San in the last hundred thousand years. “Pygmy” groups from Central African forests harbor ancestry that is arguably just as distinctive. The extremely ancient isolation of some pairs of human populations from each other conflicts with the idea that a single mutation essential to distinctively modern human behavior occurred shortly before the Upper Paleolithic and Later Stone Age. A key change essential to modern human behavior in this time frame would be expected to be at high frequency in some human populations today—those that descend from the population in which the mutation occurred—and absent or very rare in others. But this seems hard to reconcile with the fact that all people today are capable of mastering conceptual language and innovating their culture in a way that is a hallmark of modern humans.

当我们运用李和杜宾的方法寻找所有分析的基因组在旧石器时代晚期和晚期石器时代之前拥有共同祖先的位置时，基因开关概念的第二个问题就显现出来了。在FOXP2基因——根据之前的研究，该基因似乎是最有可能成为基因开关的候选基因——我们发现，所有现代人类的共同祖先（即现代人类共享的FOXP2基因拷贝最后一次出现的人）生活在一百多万年前。²⁹

A second problem with the notion of a genetic switch became apparent when we applied the Li and Durbin method to search for places where all the genomes we analyzed shared a common ancestor in the period before the Upper Paleolithic and Later Stone Age. At FOXP2—the gene that seemed the best candidate for a switch based on previous studies—we found that the common ancestor of everyone living today (that is, the person in whom modern humanity’s shared copy of FOXP2 last occurred), lived more than one million years ago.²⁹

我们将分析范围扩大到整个基因组，结果发现，除了线粒体DNA和Y染色体之外，没有任何其他区域能够证明所有现代人拥有一个共同祖先，而这个祖先的出现时间距今不过约32万年。这远远超过了克莱因假说所需的时间尺度。如果克莱因的假说正确，那么在基因组中，除了线粒体DNA和Y染色体之外，应该还存在其他区域，能够证明几乎所有人拥有一个共同祖先，而这个祖先的出现时间都在十万年之内。但事实上，这样的区域似乎并不存在。

Expanding our analysis to the whole genome, we could not find any location—apart from mitochondrial DNA and the Y chromosome—where all people living today share a common ancestor less than about 320,000 years ago. This is a far longer time scale than the one required by Klein’s hypothesis. If Klein was right, it would be expected that there would be places in the genome, beyond mitochondrial DNA and the Y chromosome, where almost everyone shares a common ancestor within the last hundred thousand years. But these do not in fact seem to exist.

我们的研究结果并未完全排除单一关键基因改变的假设。基因组中有一小部分包含难以研究的复杂序列，并未纳入我们的研究范围。但如果关键改变确实存在，那么它已无处遁形。人类基因创新和群体分化的时间尺度也远长于基因组革命之前线粒体DNA和其他基因数据所揭示的时间尺度。如果我们试图在基因组中寻找现代人类独特性的线索，那么我们很可能无法从单一或少数几个改变的解释中寻找答案。

Our results do not completely rule out the hypothesis of a single critical genetic change. There is a small fraction of the genome that contains complicated sequences that are difficult to study and that was not included in our survey. But the key change, if it exists, is running out of places to hide. The time scale of human genetic innovation and population differentiation is also far longer than mitochondrial DNA and other genetic data suggested prior to the genome revolution. If we are going to try to search the genome for clues to what makes modern humans distinctive, it is likely that we cannot look to explanations involving one or a few changes.

2000年代技术革命后出现的全基因组方法很快也表明，自然选择不太可能像克莱因设想的那样，仅仅表现为少数基因的简单变化。当第一批全基因组数据集发表后，许多遗传学家（包括我自己）开发了在基因组中搜寻受自然选择影响的突变的方法。 ³⁰我们当时在寻找“唾手可得的成果”——自然选择在少数突变上发挥强大作用的例子。这些唾手可得的成果的例子包括：例如，人类成年后仍能消化牛奶的基因突变，或是使皮肤颜色变深或变浅以适应当地气候的基因突变，又或是赋予人类对疟疾这种传染病的抵抗力的基因突变，都属于此类。作为一个群体，我们之所以能够成功地识别出这类基因突变的选择压力，是因为它们的频率从低到高迅速上升，导致如今许多人拥有共同的祖先，或者两个原本相似的人群之间存在着显著的基因突变频率差异。诸如此类的事件会在基因组变异模式上留下深刻的印记，这些印记很容易被检测到。

The whole-genome approaches that became possible after the technological revolution of the 2000s also soon made it clear that natural selection was not likely to take the simple form of changes in a small number of genes, as Klein had imagined. When the first whole-genome datasets were published, many geneticists (myself included) developed methods that scoured the genome for mutations that were affected by natural selection.³⁰ We were searching for the “low-hanging fruit”—instances in which natural selection had operated strongly on a few mutations. Examples of such low-hanging fruit include the mutations allowing people to digest cow’s milk into adulthood, or mutations that cause darkening or lightening of skin to adapt to local climates, or mutations that bequeath resistance to the infectious disease malaria. As a community, we have been successful in identifying selection on mutations like these because they have risen rapidly from low to high frequency, resulting in a large number of people today sharing a recent ancestor or striking differences in mutation frequency between two otherwise similar populations. Events like these leave great scars on patterns of genome variation that can be detected without too much trouble.

莫莉·普热沃斯基（Molly Przeworski）领导的研究抑制了人们对这一重大发现的兴奋之情。她研究了自然选择可能在整个基因组上留下的模式类型。普热沃斯基及其同事在2006年的一项研究表明，对当今人类遗传变异进行基因组扫描会遗漏大多数自然选择的例子，因为它们根本不具备检测所需的统计效力；而且，这类扫描对某些类型的选择比其他类型的选择更有检测效力。³¹她于2011年领导的一项研究随后表明，人类进化中只有一小部分可能涉及对先前群体中不存在的有利突变的强烈自然选择。 ³²因此，像促进成年后消化牛奶这样的强烈且易于检测的自然选择事件是例外。 ³³

Excitement about this bonanza was tempered by work led by Molly Przeworski, who studied the types of patterns that natural selection is likely to leave on the genome as a whole. A 2006 study by Przeworski and her colleagues showed that genome scans of present-day human genetic variation will miss most instances of natural selection because they simply will not have the statistical power needed to detect it, and that scans of this type will also have more power to detect some types of selection than others.³¹ A study she led in 2011 then showed that only a small fraction of evolution in humans has likely involved intense natural selection for advantageous mutations that had not previously been present in the population.³² Thus, intense and easily detectable episodes of natural selection such as those that have facilitated the digestion of cow’s milk into adulthood are an exception.³³

那么，如果不是选择那些新出现的、随后频率迅速上升的单次突变，人类自然选择的主要模式又是什么呢？身高研究提供了一个重要的线索。2010年，医学遗传学家分析了约18万名身高有测量数据的人的基因组，发现了180个独立的基因突变，这些突变在身材较矮的人群中更为常见。这意味着这些突变，或者基因组上附近的突变，直接导致了身高的降低。2012年，第二项研究表明，在这180个突变中，南欧人往往携带那些导致身高降低的突变版本，而且这种模式非常显著，唯一可能的解释就是自然选择——可能是因为北欧人身高增加，或者南欧人身高降低，因为这两个谱系已经^分离。2015年，我实验室的伊恩·马西森（Iain Mathieson）领导的一项古DNA研究揭示了更多关于这一过程的信息。我们收集了230位古代欧洲人的骨骼和牙齿的DNA数据，并进行分析，结果表明，这些模式反映了自然选择对某些突变的适应性作用。这些突变导致8000年前之后南欧农民的身高降低，或5000年前生活在东欧草原地区的北欧祖先的身高增加。 ³⁵南欧矮个子或远东欧高个子所获得的优势，必然增加了他们后代的存活数量，从而系统性地改变了这些突变的频率，最终达到一个新的平均身高。

So what has been the dominant mode of natural selection in humans if not selection on newly arising single mutation changes that then rocket up to high frequency? An important clue comes from the study of height. In 2010, medical geneticists analyzed the genomes of around 180,000 people with measured heights, and found 180 independent genetic changes that are more common in shorter people. This means that these changes, or ones nearby on the genome, contribute directly to reduced height. In 2012, a second study showed that at the 180 changes, southern Europeans tend to have the versions that reduce height, and that this pattern is so pronounced that the only possible explanation is natural selection—likely for increased height in northern Europeans or decreased height in southern Europeans since the two lineages separated.³⁴ In 2015, an ancient DNA study led by Iain Mathieson in my laboratory revealed more about this process. We assembled DNA data from the bones and teeth of 230 ancient Europeans and analyzed the data to suggest that these patterns reflected natural selection for mutations that decreased height in farmers in southern Europe after eight thousand years ago, or increased height in ancestors of northern Europeans who lived in the eastern European steppe lands before five thousand years ago.³⁵ The advantages that accrued to shorter people in southern Europe, or to taller people in far eastern Europe, must have increased the number of their surviving children, which had the effect of systematically changing the frequencies of these mutations until a new average height was achieved.

自身高研究发现以来，其他科学家也记录了自然选择对其他复杂人类特征的更多影响。2016 年的一项研究分析了数千名当代英国人的基因组，发现自然选择有利于身高增加、金发、蓝眼睛、婴儿头围增大、女性臀围增大、男性生长突增延迟以及女性青春期延迟。 ³⁶

Since the discoveries about height, other scientists have documented additional examples of natural selection on other complex human traits. A 2016 study analyzed the genomes of several thousand present-day Britons and found natural selection for increased height, blonder hair, bluer eyes, larger infant head size, larger female hip size, later growth spurt in males, and later age of puberty in females.³⁶

这些例子表明，通过利用全基因组的力量同时检测基因组中数千个独立位点，我们可以突破莫莉·普热沃斯基（Molly Przeworski）提出的“普热沃斯基极限”（Przeworski's Limit）。这得益于我们现在掌握的关于基因组中许多位点上具有相似生物学效应的大量遗传变异的信息。我们从“全基因组关联研究”（GWAS）中获得了这些信息。自2005年以来，GWAS已收集了超过一百万人的各种测量性状的数据，从而识别出超过一万个在具有特定性状（包括身高）的人群中频率显著升高的突变。 ³⁷全基因组关联研究对于理解人类健康和疾病的价值一直存在争议，因为这些研究识别出的特定突变通常影响很小，其结果几乎无法用于预测谁会患病，谁不会患病。 ³⁸但人们常常忽略的是，全基因组关联研究为研究人类随时间推移的进化变化提供了一个强大的资源。通过检验已识别出的突变是否与人类的进化变化相关，我们可以更好地了解人类的进化历程。全基因组关联研究表明，影响特定生物性状的频率都趋向于同一方向变化，由此我们可以获得特定生物性状自然选择的证据。

These examples demonstrate that by leveraging the power of the whole genome to examine thousands of independent positions in the genome simultaneously, it is possible to get beyond the barrier that Molly Przeworski had identified—“Przeworski’s Limit”—by taking advantage of information that we now have about a large number of genetic variations at many locations in the genome that have similar biological effects. We have such information from “genome-wide association studies,” which since 2005 have collected data from more than one million people with a variety of measured traits, thereby identifying more than ten thousand individual mutations that occur at significantly elevated frequency in people with particular traits, including height.³⁷ The value of genome-wide association studies for understanding human health and disease has been contentious because the specific mutation changes that these studies have identified typically have such small effects that their results are hardly useful for predicting who gets a disease and who does not.³⁸ But what is often overlooked is that genome-wide association studies have provided a powerful resource for investigating human evolutionary change over time. By testing whether the mutations identified by genome-wide association studies as affecting particular biological traits have all tended to shift in frequency in the same direction, we can obtain evidence of natural selection for specific biological traits.

随着全基因组关联研究的深入，人们开始探索人类认知和行为特征的变异，³⁹而诸如此类的研究——例如身高研究——将使我们能够探究祖先行为向现代性转变是否由自然选择驱动。这意味着，我们有望从遗传学的角度解开困扰克莱因的谜团——旧石器时代晚期和新石器时代晚期考古记录所揭示的人类行为的巨大变化。

As genome-wide association studies proceed, they are beginning to investigate human variation in cognitive and behavioral traits,³⁹ and studies like these—such as the ones for height—will make it possible to explore whether the shift to behavioral modernity among our ancestors was driven by natural selection. This means that there is new hope for providing genetic insight into the mystery that puzzled Klein—the great change in human behavior suggested by the archaeological records of the Upper Paleolithic and Later Stone Age.

但即便基因变化——通过协调的自然选择同时作用于多种突变组合——确实促成了新的认知能力，这也与克莱因提出的“基因开关”概念截然不同。在这种情况下，基因变化并非突然赋予现代人类行为的创造性力量，而是对来自外部的非遗传压力做出的响应。在这种情境下，并非人类群体因为无人携带赋予某种先前不存在的生物能力的突变而无法适应。相反，驱动旧石器时代晚期和后石器时代人类行为和能力显著进步的基因公式并非神秘莫测。促成现代人类行为所需的突变早已存在，而由于概念语言发展或新环境条件带来的不断变化的需求，自然选择可能导致这些突变的多种组合频率同时增加。这反过来又可能促成生活方式和创新的进一步变革，形成一个自我强化的循环。因此，即使突变频率的增加确实对现代人类在旧石器时代晚期和新石器时代过渡时期适应新环境至关重要，但我们现在对人类自然选择本质以及许多生物性状的基因编码的了解表明，这些突变的首次出现不太可能是引发随后巨大变化的直接原因。如果我们试图在少数几个近期出现的突变中寻找答案，那么……在旧石器时代晚期和新石器时代晚期过渡时期之前，我们不太可能找到关于我们是谁的令人满意的解释。

But even if genetic changes—through coordinated natural selection on combinations of many mutations simultaneously—did enable new cognitive capacities, this is a very different scenario from Klein’s idea of a genetic switch. Genetic changes in this scenario are not a creative force abruptly enabling modern human behavior, but instead are responsive to nongenetic pressures imposed from the outside. In this scenario, it is not the case that the human population was unable to adapt because no one carried a mutation that allows a biological capability not previously present. Instead, the genetic formula that may have been necessary to drive the striking advances in human behavior and capacities that occurred during the Upper Paleolithic and Later Stone Ages is not particularly mysterious. The mutations necessary to facilitate modern human behavior were already in place, and many alternative combinations of these mutations could have increased in frequency together due to natural selection in response to changing needs imposed by the development of conceptual language or new environmental conditions. This in turn could have enabled further changes in lifestyle and innovation, in a self-reinforcing cycle. Thus, even if it is true that increases in the frequency of mutations were important in allowing modern humans to match their biology to new conditions during the Upper Paleolithic and Later Stone Age transition, what we now know about the nature of natural selection in humans and about the genetic encoding of many biological traits means it is unlikely that the first occurrence of these mutations triggered the great changes that followed. If we search for answers in a small number of mutations that arose shortly before the time of the Upper Paleolithic and Later Stone Age transitions, we are unlikely to find satisfying explanations of who we are.

基因组如何解释我们是谁

How the Genome Can Explain Who We Are

分子生物学家率先将基因组学的力量应用于人类进化研究。或许正是由于他们的背景——以及他们以往运用还原论方法破解生命奥秘（例如遗传密码）的辉煌战绩——分子生物学家们满怀希望地认为，遗传学能够揭示人类与其他动物在生物学上的差异。考古学家和公众也同样对这一前景充满期待。然而，这项研究计划虽然意义重大，但仍处于起步阶段，因为答案绝非易事。

It was molecular biologists who first focused the power of the genome onto the study of human evolution. Perhaps because of their background—and their track record of using reductionist approaches to solve great mysteries of life like the genetic code—molecular biologists were motivated by the hope that genetics would provide insights into the biological nature of how humans differ from other animals. Excitement about this prospect has also been shared by archaeologists and the public. But this research program, important as it is, is still at its very beginning because the answer is not going to be simple.

基因组革命在揭示人类迁徙而非解释人类生物学方面已经取得了巨大的成功。近几年来，在古代DNA的推动下，基因组革命揭示了人类群体之间前所未有的关联。这与我们儿时所学的或流行文化中的故事截然不同。它充满了惊喜：不同人群的大规模融合；人口的彻底更替和扩张；以及史前时期与当今人口差异截然不同的人口划分。这是一个关于我们这个相互联系的人类大家庭如何以无数种我们从未想象过的方式形成的传奇故事。

It is in the area of shedding light on human migrations—rather than in explaining human biology—that the genome revolution has already been a runaway success. In the last few years, the genome revolution—turbocharged by ancient DNA—has revealed that human populations are related to each other in ways that no one expected. The story that is emerging differs from the one we learned as children, or from popular culture. It is full of surprises: massive mixtures of differentiated populations; sweeping population replacements and expansions; and population divisions in prehistoric times that did not fall along the same lines as population differences that exist today. It is a story about how our interconnected human family was formed, in myriad ways never imagined.

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与尼安德特人的接触

Encounters with Neanderthals

尼安德特人和现代人的相遇

The Meeting of Neanderthals and Modern Humans

如今，我们所属的人类特定亚群——现代人类——是地球上唯一的人类。我们通过竞争或灭绝其他人类，主要发生在大约五万年前之后，当时现代人类扩张至整个欧亚大陆，非洲内部也可能发生了大规模的人类迁徙。如今，我们现存的近亲是非洲猿类：黑猩猩、倭黑猩猩和大猩猩，它们都无法制造复杂的工具或使用概念性语言。但在大约四万年前，地球上曾居住着多个古人类群体，他们在体格上与我们有所不同，但能够直立行走，并拥有许多与我们相同的能力。考古记录无法解答——但DNA记录可以解答——这些古人类与我们之间的亲缘关系。

Today, the particular subgroup of humans to which we belong—modern humans—is alone on our planet. We outcompeted or exterminated other humans, mostly during the period after around fifty thousand years ago when modern humans expanded throughout Eurasia and when major movements of humans likely happened within Africa too. Today, our closest living relatives are the African apes: the chimpanzees, bonobos, and gorillas, all incapable of making sophisticated tools or using conceptual language. But until around forty thousand years ago, the world was inhabited by multiple groups of archaic humans who differed from us physically but walked upright and shared many of our capabilities. The question that the archaeological record cannot answer—but the DNA record can—is how those archaic people were related to us.

对于任何远古人类群体而言，这个问题的答案似乎都比尼安德特人更为迫切。四十万年前的欧洲，这片土地曾被这些体型庞大、平均脑容量略大于现代人类的人类所主宰。1856年，矿工们在尼安德河谷（德语中“河谷”一词为Thal或Tal）的一处石灰岩采石场发现了赋予尼安德特人这一名称的化石。多年来，关于这些遗骸究竟属于畸形人类还是人类，一直争论不休。祖先，或者说与我们自身人类谱系差异极大的人类血统。尼安德特人是科学界最早确认的古人类。在1871年出版的《人类的由来》一书中，查尔斯·达尔文论证说，人类和其他动物一样^，都是进化的产物。尽管达尔文本人并未意识到尼安德特人的重要性，但最终人们认识到，尼安德特人与现代人类的亲缘关系比与现存猿类更近，这为达尔文的理论提供了证据，即过去必然存在过这样的古人类群体。

For no archaic group has the answer to this question seemed more urgent than for the Neanderthals. In Europe after four hundred thousand years ago, the landscape was dominated by these large-bodied people with brains slightly bigger on average than those of modern humans. The specimen that gave its name to Neanderthals was found in 1856 by miners in a limestone quarry in the Neander Valley (the German word for valley is Thal or Tal). For years, debate raged over whether these remains came from a deformed human, a human ancestor, or a human lineage that is extremely divergent from our own. Neanderthals became the first archaic humans to be recognized by science. In The Descent of Man, published in 1871, Charles Darwin argued that humans are like other animals in that they are also the products of evolution.¹ Although Darwin didn’t himself appreciate their significance, Neanderthals were eventually acknowledged to be from a population more closely related to modern humans than to living apes, providing evidence for Darwin’s theory that such populations must have existed in the past.

在接下来的一个半世纪里，人们发现了许多尼安德特人的骨骼。这些研究表明，尼安德特人是由更古老的人类在欧洲进化而来。在流行文化中，他们被描绘成野蛮人，与我们人类的差异远大于实际情况。这种原始的印象很大程度上源于1911年法国拉沙佩勒圣地出土的尼安德特人骨骼的复原图，该图将尼安德特人的姿势扭曲变形。但根据我们掌握的所有证据，大约在十万年前，尼安德特人的行为与我们的祖先——解剖学意义上的现代人类——一样复杂。

Over the next century and a half there were discoveries of many additional Neanderthal skeletons. These studies revealed that Neanderthals had evolved in Europe from even more archaic humans. In popular culture, they garnered a reputation as beastly—much more different from us than they in fact were. The primitive reputation of Neanderthals was fueled in large part by a slouched reconstruction of the Neanderthal skeleton from La Chapelle-aux-Saints, France, made in 1911. But from all the evidence we have, before about one hundred thousand years ago, Neanderthals were behaviorally just as sophisticated as our own ancestors—anatomically modern humans.

尼安德特人和解剖学意义上的现代人都使用一种被称为勒瓦卢瓦（Levallois）的石器制作技术。这种技术对认知能力和灵巧度的要求，与大约五万年前现代人出现的旧石器时代晚期和晚期石器时代的工具制作技术不相上下。在勒瓦卢瓦技术中，工匠们从精心准备的岩芯上敲击出石片，这些岩芯与最终成品几乎没有相似之处。因此，工匠们必须在脑海中预先构思出最终工具的形态，并执行一系列复杂的石器加工步骤，才能最终达到预期的效果。

Both Neanderthals and anatomically modern humans made stone tools using a technique that has become known as Levallois, which requires as much cognitive skill and dexterity as the Upper Paleolithic and Later Stone Age toolmaking techniques that emerged among modern humans after around fifty thousand years ago. In this technique, flakes are struck off carefully prepared rock cores that have little resemblance to the resulting tools, so that craftspeople must hold in their minds an image of what the finished tool will look like and execute the complex steps by which the stone must be worked to achieve that goal.

尼安德特人认知能力高的其他迹象还包括他们照顾病人和老人的证据。在伊拉克沙尼达尔洞穴的一次挖掘中，发现了九具骨骼，显然都是被故意埋葬的，其中一具是一位半盲老人，手臂萎缩，这表明他能够存活下来的唯一途径就是得到亲朋好友的悉心照料。 ²尼安德特人也懂得欣赏象征意义，克罗地亚克拉皮纳洞穴发现的用鹰爪制成的首饰就证明了这一点，这些首饰的年代可以追溯到公元前约1000年。距今约13万年前，法国布鲁尼凯尔洞穴深处建造了^{3座石圈，其历史可追溯至约18万年前。}

Other signs of the cognitive sophistication of Neanderthals include the evidence that they cared for their sick and elderly. An excavation at Shanidar Cave in Iraq has revealed nine skeletons, all apparently deliberately buried, one of which was a half-blind elderly man with a withered arm, suggesting that the only way he could have survived is if friends and family had lovingly cared for him.² The Neanderthals also had an appreciation of symbolism, as revealed by jewelry made of eagle talons found at Krapina Cave in Croatia and dating to about 130,000 years ago,³ and stone circles built deep inside Bruniquel Cave in France and dating to around 180,000 years ago.⁴

尽管尼安德特人和现代人之间存在诸多相似之处，但显著的差异也显而易见。一篇写于20世纪50年代的文章声称，如果一个尼安德特人在纽约地铁上出现，“只要他洗干净澡、刮干净胡子、穿上现代服装”，就不会引起任何人的注意。⁵^但事实上，他或她奇特的突出眉骨和令人印象深刻的肌肉发达的体格会暴露其身份。尼安德特人与当今任何人类群体之间的差异，远大于现代不同人群之间的差异。

Yet despite similarities between Neanderthals and modern humans, profound differences are evident. An article written in the 1950s claimed that a Neanderthal on the New York City subway would attract no attention, “provided that he were bathed, shaved, and dressed in modern clothing.”⁵ But in truth, his or her strangely projecting brow and impressively muscular body would be giveaways. Neanderthals were much more different from any human population today than present-day populations are from each other.

尼安德特人和现代人的相遇也激发了小说家的想象力。在威廉·戈尔丁1955年的小说《继承者》中，一群尼安德特人被现代人杀死，现代人收养了一个幸存的尼安德特孩子。 ⁶在简·奥尔1980年的小说《洞熊部落》中，一位现代女性被尼安德特人抚养长大，这本书的构思在于戏剧化地展现了这两个高度发达的人类群体——彼此如此陌生却又如此相似——之间密切互动的情景。 ⁷

The encounter of Neanderthals and modern humans has also captured the imagination of novelists. In William Golding’s 1955 The Inheritors, a band of Neanderthals is killed by modern humans, who adopt a surviving Neanderthal child.⁶ In Jean Auel’s 1980 The Clan of the Cave Bear, a modern human woman is brought up by Neanderthals, and the conceit of the book is a dramatization of what close interaction of these two sophisticated groups of humans, so alien to each other and yet so similar, might have been like.⁷

有确凿的科学证据表明现代人类和尼安德特人曾有过接触。最直接的证据来自西欧，尼安德特人大约在三万九千年前在那里消失。8^现代人类抵达西欧的时间至少比尼安德特人早几千年，意大利南部富马内遗址就证明了这一点。大约四万四千年前，尼安德特人使用的石器逐渐被现代人类的典型工具所取代。在西南欧，考古学家在距今四万四千年至三万九千年的尼安德特人遗骸中发现了现代人类制造的典型工具，这些工具的制作风格被称为沙特尔佩龙文化。这表明尼安德特人可能模仿了现代人类的工具制作工艺，或者这两个群体之间可能进行过工具或材料的贸易。然而，并非所有考古学家都接受这种解释，关于沙特尔佩龙文化的器物究竟是由尼安德特人还是现代人类制造的，目前仍存在争议^。9

There is hard scientific evidence that modern humans and Neanderthals met. The most direct is from western Europe, where Neanderthals disappeared around thirty-nine thousand years ago.⁸ The arrival of modern humans in western Europe was at least a few thousand years earlier, as is evident at Fumane in southern Italy where around forty-four thousand years ago, Neanderthal-type stone tools gave way to tools typical of modern humans. In southwestern Europe, tools typical of modern humans, made in a style called Châtelperronian, have been found amidst Neanderthal remains that date to between forty-four thousand and thirty-nine thousand years ago, suggesting that Neanderthals may have imitated modern human toolmaking, or that the two groups traded tools or materials. Not all archaeologists accept this interpretation, though, and there is ongoing debate about whether Châtelperronian artifacts were made by Neanderthals or by modern humans.⁹

尼安德特人和现代人类的相遇不仅发生在欧洲，而且几乎可以肯定也发生在近东。大约七万年前，一支强大而繁荣的尼安德特人种群从欧洲扩张到中亚。远至阿尔泰山脉，并进入近东地区。近东地区早已有现代人类居住，以色列卡梅尔山脊的斯库尔洞穴和下加利利的卡夫泽洞穴中发现的遗骸证实了这一点，这些遗骸的年代可追溯到大约13万至10万年前。 ¹⁰ 后来，尼安德特人迁徙到该地区，卡梅尔山脊凯巴拉洞穴中发现的一具骨骼的年代可追溯到6万至4.8万年前。 ¹¹这颠覆了我们可能认为现代人类取代了……的预期。在每一次与现代人类的遭遇中，尼安德特人都从他们的故乡（欧洲）向外扩张，而现代人类则不断撤退。然而，大约在六万年前，现代人类开始在近东地区占据主导地位。此时，尼安德特人在这场遭遇中败下阵来，他们不仅在近东地区灭绝，最终也在欧亚大陆的其他地区灭绝。因此，在近东地区，尼安德特人和现代人类至少有过两次相遇：一次是大约十万年前，早期现代人类首次定居该地区，并建立了自己的族群，与不断扩张的尼安德特人相遇；另一次是大约在六万至五万年前，现代人类再次返回该地区，并将尼安德特人取代。

Meetings between Neanderthals and modern humans took place not only in Europe but almost certainly in the Near East as well. After around seventy thousand years ago, a strong and successful Neanderthal population expanded from Europe into central Asia as far as the Altai Mountains, and into the Near East. The Near East had already been inhabited by modern humans, as attested by remains at Skhul Cave on the Carmel Ridge in Israel and Qafzeh Cave in the Lower Galilee dating to between about 130,000 and 100,000 years ago.¹⁰ Later, Neanderthals moved into the region, with one skeleton at Kebara Cave on the Carmel Ridge dating to between sixty and forty-eight thousand years ago.¹¹ Reversing the expectation we might have that modern humans displaced Neanderthals at every encounter, Neanderthals were advancing from their homeland (Europe) even as modern humans retreated. Sometime after sixty thousand years ago, though, modern humans began to predominate in the Near East. Now the Neanderthals were the losers in the encounter, and they went extinct not only in the Near East but eventually elsewhere in Eurasia as well. So it was that in the Near East there were at least two opportunities for encounters between Neanderthals and modern humans: when early modern humans first peopled the region before around one hundred thousand years ago and established a population that met the expanding Neanderthals, and when modern humans returned and displaced the Neanderthals there sometime around sixty or fifty thousand years ago.

这两个人群是否杂交过？尼安德特人是否是现代人类的直系祖先？一些骨骼证据表明存在杂交现象。埃里克·特林考斯（Erik Trinkaus）鉴定出一些遗骸，例如罗马尼亚绿洲洞穴（Oase Cave）中的遗骸，他认为这些遗骸介于现代人类和尼安德特人之间。 ¹²然而，相似的骨骼特征有时反映的是对相同环境压力的适应，而非共同的祖先。这就是为什么考古和骨骼记录无法确定尼安德特人与我们的亲缘关系。基因组研究可以做到这一点。

Did the two populations interbreed? Are the Neanderthals among the direct ancestors of any present-day humans? There is some skeletal evidence for hybridization. Erik Trinkaus identified remains such as those from Oase Cave in Romania that he argued were intermediate between modern humans and Neanderthals.¹² However, shared skeletal features sometimes reflect adaptation to the same environmental pressures, not shared ancestry. This is why archaeological and skeletal records cannot determine the relatedness of Neanderthals to us. Studies of the genome can.

尼安德特人DNA

Neanderthal DNA

早期，研究古代DNA的科学家几乎完全专注于线粒体DNA，原因有二。首先，每个细胞中大约有一千份线粒体DNA拷贝，而基因组其他大部分区域只有两份拷贝，这增加了成功提取线粒体DNA的几率。其次，线粒体DNA信息丰富：在给定数量的DNA碱基对中，其差异远多于基因组其他区域，这使得对每个成功分析的DNA碱基对进行更精确的遗传分离时间测量成为可能。线粒体数据分析证实，尼安德特人与现代人类的母系共同祖先比之前认为的更近。13.目前最佳估计是距今47万至36万年前。14 ^.线粒体DNA分析也证实，尼安德特人具有高度独特性。他们的DNA类型超出了现代人类的变异范围，与我们拥有共同祖先，其年代比“线粒体夏娃”生活的年代要古老数倍。15 ^.

Early on, scientists studying ancient DNA focused almost exclusively on mitochondrial DNA, for two reasons. First, there are about one thousand copies of mitochondrial DNA in each cell, compared to two copies of most of the rest of the genome, increasing the chance of successful extraction. Second, mitochondrial DNA is information-dense: there are many more differences for a given number of DNA letters than in most other places in the genome, making it possible to obtain a more precise measurement of genetic separation time for every letter of DNA that is successfully analyzed. Mitochondrial data analysis confirmed that Neanderthals shared maternal-line ancestors with modern humans more recently than previously thought¹³—the best current estimate is 470,000 to 360,000 years ago.¹⁴ Mitochondrial DNA analysis also confirmed that the Neanderthals were highly distinctive. Their DNA type was outside the range of present-day variation in humans, sharing a common ancestor with us at a date several times more ancient than the time when “Mitochondrial Eve” lived.¹⁵

尼安德特人的线粒体DNA并未提供任何证据支持尼安德特人和现代人类相遇时曾杂交的理论，但同时，线粒体DNA证据也无法排除现代非非洲人群DNA中约有25%的尼安德特人基因构成。 ¹⁶我们仅凭线粒体DNA难以对现代人类的尼安德特人基因构成做出确切判断，这是有原因的。即使如今非洲以外的现代人类确实拥有相当数量的尼安德特人血统，但当时只有极少数女性幸运地将她们的线粒体DNA遗传给了现代人。如果这些女性中的大多数是现代人，那么我们今天看到的基因模式也就不足为奇了。因此，线粒体数据并不具有决定性意义，但尼安德特人和现代人类没有混血的观点仍然是科学界的正统观念，直到斯万特·帕博的团队从尼安德特人的整个基因组中提取出DNA，才使得研究其所有祖先的历史成为可能，而不仅仅是母系血统。

Neanderthal mitochondrial DNA provided no support for the theory that Neanderthals and modern humans interbred when they encountered each other, but at the same time the mitochondrial DNA evidence could not exclude up to around a 25 percent contribution of Neanderthals to the DNA of present-day non-Africans.¹⁶ There is a reason why we have so little power to make statements about the Neanderthal contribution to modern humans based only on mitochondrial DNA. Even if modern humans outside Africa today do have substantial Neanderthal ancestry, there are only one or few women who lived at that time and were lucky enough to pass down their mitochondrial DNA to present-day people, and if most of those women were modern humans, the patterns we see today would not be surprising. So the mitochondrial data were not conclusive, but nevertheless the view that Neanderthals and modern humans did not mix remained the scientific orthodoxy until Svante Pääbo’s team extracted DNA from the whole genome of a Neanderthal, making it possible to examine the history of all its ancestors, not just the exclusively maternal line.

在尼安德特人线粒体 DNA 测序之后的十年里，古代 DNA 研究技术的效率取得了巨大飞跃，这使得对整个尼安德特人基因组进行测序成为可能。

The advance to sequencing the whole Neanderthal genome was made possible by a huge leap in the efficiency of the technology for studying ancient DNA in the decade after the sequencing of Neanderthal mitochondrial DNA.

2010年以前，古代DNA研究的主要手段是聚合酶链式反应（PCR）。该方法首先选择一段DNA作为靶标，然后合成与靶标片段两侧基因组序列相匹配的、长度约为20个碱基对的DNA片段。这些独特的片段能够识别出基因组中的目标部分，然后通过酶进行多次复制。最终，样本中极小一部分DNA序列会成为主要序列。然而，这种方法会丢弃绝大多数DNA。（非目标部分）。尽管如此，它至少可以提取出一些感兴趣的DNA。

The mainstay of ancient DNA research prior to 2010 was a technique called polymerase chain reaction (PCR). This involved selecting a stretch of DNA to be targeted, and then synthesizing approximately twenty-letter-long fragments of DNA that match the genome on each side of the targeted segment. These unique fragments pick out the targeted part of the genome, which is then duplicated many times over by enzymes. The effect is to take a tiny fraction of all the DNA in the sample and make it the dominant sequence. This method throws away the vast majority of DNA (the part that is not targeted). Nevertheless, it can extract at least some DNA that is of interest.

提取古代DNA的新方法截然不同。它依赖于对样本中所有DNA进行测序，无论其来自基因组的哪个部分，也无需预先根据靶序列选择DNA。这种方法充分利用了新型测序仪的强大计算能力，这些仪器在2006年至2010年间将测序成本降低了至少一万倍。计算机可以分析这些数据，从而拼凑出大部分基因组，或者从中筛选出目标基因。

The new approach for extracting ancient DNA was radically different. It relied on sequencing all of the DNA in the sample, regardless of the part of the genome it comes from, and without preselecting the DNA based on targeting sequences. It took advantage of the brute power of new machines, which from 2006 to 2010 reduced the cost of sequencing by at least about ten thousandfold. The data could be analyzed by a computer to piece together most of a genome, or alternatively to pick out a gene of interest.

为了使新方法奏效，帕博的团队需要克服几个挑战。首先，他们需要找到一块能够提取足够DNA的骨骼。人类学家通常研究化石——完全矿化成岩石的骨骼。但从真正的化石中提取DNA是不可能的。因此，帕博寻找的是那些尚未完全矿化但含有有机物质的骨骼，其中包括保存完好的DNA片段。其次，假设团队能够找到一块保存完好的“黄金样本”，他们仍然需要解决样本被微生物DNA污染的问题。微生物DNA来自死后寄生在骨骼中的细菌和真菌。在大多数古代样本中，这些微生物贡献了绝大部分的DNA。最后，团队还必须考虑研究人员（考古学家或分子生物学家）处理样本和化学试剂时可能造成的污染，因为他们可能在样本上留下了自身DNA的痕迹。

To make the new approach work, Pääbo’s team needed to overcome several challenges. First, they needed to find a bone from which they could extract enough DNA. Anthropologists often work with fossils—bones completely mineralized into rocks. But it is impossible to get any DNA from a true fossil. Pääbo was therefore looking for bones that were not completely mineralized but contained organic material, including stretches of well-preserved DNA. Second, supposing the team could find a “golden sample” with well-preserved DNA, they still had to overcome the problem of contamination of the sample by microbial DNA, which comes from the bacteria and fungi that embed themselves in bone after an individual’s death. These contribute the overwhelming majority of DNA in most ancient samples. Finally, the team had to consider the likelihood of contamination by the researchers—archaeologists or molecular biologists—who handled the samples and chemicals and may have left traces of their own DNA on them.

污染是古代人类DNA研究的一大隐患。受污染的序列会误导分析人员，因为接触骨骼的现代人与被测序的个体之间存在亲缘关系，即使这种亲缘关系非常遥远。从保存完好的样本中提取的典型尼安德特人古代DNA片段只有大约40个碱基对，而现代人和尼安德特人之间的差异率约为每600个碱基对一个，因此有时根本无法判断一段特定的DNA序列是来自骨骼本身，还是来自接触过骨骼的人。污染问题一直困扰着古代DNA研究人员。例如，2006年，帕博的研究小组对来自尼安德特人的大约一百万个碱基对的DNA进行了测序。在进行全基因组测序之前，对尼安德特人进行了试验性测序。 ¹⁷但其中很大一部分序列是现代人类的污染序列，影响了数据的解读。 ¹⁸

Contamination is a huge danger for studies of ancient human DNA. Contaminated sequences can mislead analysts because the modern humans handling the bone are related, even if very distantly, to the individual being sequenced. A typical Neanderthal ancient DNA fragment from a well-preserved sample is only about forty letters long, while the rate of differences between modern humans and Neanderthals is about one per six hundred letters, so it is sometimes impossible to tell whether a particular stretch of DNA comes from the bone or from someone who handled it. Contamination has bedeviled ancient DNA researchers time and again. For example, in 2006 Pääbo’s group sequenced about a million letters of DNA from Neanderthals as a trial run prior to whole-genome sequencing.¹⁷ A high fraction of the sequences were modern human contaminants, compromising interpretation of the data.¹⁸

为了最大限度地减少古代DNA分析中污染的可能性，现代措施已在2006年的一项研究中开始实施，并在之后变得更加精细，这些措施包含一系列极其严苛的预防措施。在2010年帕博及其团队成功测序未受污染的尼安德特人基因组的研究中，他们将筛选的每一块骨骼都带入一个“洁净室”，该洁净室的设计参考了计算机行业微芯片制造车间的洁净空间。洁净室上方安装了与手术室相同的紫外线灯，在研究人员不在场时开启，以将污染的DNA转化为无法测序的形式（紫外线灯也会破坏样本表面的古代DNA，但研究人员会钻取样本，因此能够获取未被破坏的DNA）。此外，洁净室内的空气经过超滤处理，以去除可能含有DNA的微小灰尘颗粒——任何比人类头发丝直径小一千倍以上的颗粒。该套房采用加压设计，使空气从内部流向外部，以保护样本免受实验室外部飘入的任何污染性 DNA 的侵害。

Modern measures to minimize the possibility of contamination in ancient DNA analysis, which had already begun to be implemented in the 2006 study and which became even more elaborate afterward, involve an obsessive set of precautions. For the 2010 study in which Pääbo and his team successfully sequenced an uncontaminated Neanderthal genome, they took each of the bones they screened into a “clean room,” which they adapted from the blueprints of the clean spaces used in microchip fabrication facilities in the computer industry. There was an overhead ultraviolet (UV) light of the same type used in surgical operating suites that was turned on whenever researchers were not present, in order to convert contaminating DNA into a form that cannot be sequenced (the light also destroys ancient DNA on the outside of samples, but researchers drill beneath the surface and so are able to access DNA that is not destroyed). The air was ultra-filtered to remove tiny dust particles—anything more than one thousand times smaller than the width of a human hair—that might contain DNA. The suite was pressurized so that air flowed from inside to outside, to protect the samples from any contaminating DNA wafting in from outside the lab.

套房内设有三个独立的房间。在第一个房间里，研究人员穿上全身防护服，戴上手套和口罩。在第二个房间里，他们将选定的骨骼样本放入一个舱室，用高能紫外线照射骨骼，目的是将可能存在于骨骼表面的污染性DNA转化为无法测序的形式。随后，研究人员使用消毒过的牙钻钻取骨骼样本，将数十或数百毫克的粉末收集到经紫外线照射的铝箔上，并将这些粉末放入经紫外线照射的试管中。在第三个房间里，他们将粉末浸入去除骨骼矿物质和蛋白质的化学溶液中，然后将溶液流过纯沙（二氧化硅）。在合适的条件下，二氧化硅可以结合DNA，同时去除干扰测序化学反应的化合物。

There were three separate rooms in the suite. In the first, the researchers donned full-body clean suits, gloves, and face masks. In the second, they placed the bones chosen for sampling into a chamber where they were exposed to high-energy UV radiation, again with the goal of converting the contaminating DNA that might be lying on the surface into a form that cannot be sequenced. The researchers then cored the bones using a sterilized dental drill, collected tens or hundreds of milligrams of powder onto UV-irradiated aluminum foil, and deposited this powder into a UV-irradiated tube. In the third chamber, they immersed the powder into chemical solutions that removed bone minerals and protein, and ran the solution over pure sand (silicon dioxide), which under the right conditions binds the DNA while removing the compounds that poison the chemical reactions used for sequencing.

研究人员随后对所得的DNA片段进行了转化。他们将DNA片段转化为可测序的形式。首先，他们用化学方法去除DNA片段末端因埋藏于地下数万年而降解的残端。为了进一步去除污染，Pääbo及其团队在2006年的研究基础上，在DNA片段的末端连接了一段人工合成的字母序列，即化学“条形码”。这样，任何在连接条形码后进入实验的污染序列都可以与古代样本的DNA区分开来。最后一步是在DNA片段的两端连接分子接头，以便在新型测序仪上进行测序。这些新型测序仪的成本比以往的技术降低了数万倍。

The researchers then transformed the resulting DNA fragments into a form that could be sequenced. First, they chemically removed the ragged ends of the DNA fragments that had been degraded after tens of thousands of years buried under the ground. In an extra measure to remove contamination beyond what had been done in the 2006 study, Pääbo and his team attached an artificially synthesized sequence of letters, a chemical “barcode,” to the ends of the DNA fragments. Any contaminating sequences that entered the experiment after the attachment of the barcode could thus be distinguished from the DNA of the ancient sample. The final step was to attach molecular adapters at either end that allowed the DNA fragment to be sequenced in one of the new machines that had made sequencing tens of thousands of times cheaper than the previous technology.

保存最完好的尼安德特人样本是来自克罗地亚高地温迪亚洞穴的三块距今约四万年的臂骨和腿骨。帕博的团队对这些骨骼进行测序后发现，他们获得的绝大多数DNA片段都来自曾经寄生在骨骼上的细菌和真菌。但是，通过将数百万个片段与现代人类和黑猩猩的基因组序列进行比较，他们从这些“渣滓”中发现了宝贵的信息。这些参考基因组就像拼图盒上的图案，为他们匹配测序的微小DNA片段提供了关键线索。这些骨骼中含有高达4%的古人类DNA。

The best-preserved Neanderthal samples turned out to be three approximately forty-thousand-year-old arm and leg bones from Vindija Cave in the highlands of Croatia. After sequencing from these bones, Pääbo’s team found that the great majority of DNA fragments they obtained were from bacteria and fungi that had colonized the bones. But by comparing the millions of fragments to the present-day human and chimpanzee genome sequences, they found gold amidst the dross. These reference genomes were like the picture on a jigsaw puzzle box, providing the key to aligning the tiny fragments of DNA they had sequenced. The bones contained as much as 4 percent archaic human DNA.

2007年，帕博意识到他几乎可以完成整个尼安德特人基因组的测序，于是组建了一支国际专家团队，以确保分析结果能够充分反映数据的真实性。我和我的主要科研伙伴——应用数学家尼克·帕特森——就是这样参与进来的。帕博之所以联系我们，是因为在过去的五年里，我们在人口混合研究领域已确立了创新者的地位。在多次前往德国的行程中，我为最终证实尼安德特人和部分现代人类之间存在杂交的分析工作做出了重要贡献。

Once Pääbo realized in 2007 that he would be able to sequence almost the entire Neanderthal genome, he assembled an international team of experts with the goal of ensuring that the analysis would do justice to the data. This is how I got involved, together with my chief scientific partner, the applied mathematician Nick Patterson. Pääbo reached out to us because over the previous five years we had established ourselves as innovators in the area of studying population mixture. Over the course of many trips to Germany, I played an important role in the analyses that proved interbreeding between Neanderthals and some modern humans.

尼安德特人与非非洲人之间的亲缘关系

Affinities Between Neanderthals and Non-Africans

我们使用过的尼安德特人基因组序列错误百出，这令人遗憾。数据表明，在尼安德特人和现代人从共同祖先分离后，尼安德特人谱系上的突变数量是现代人谱系的数倍，因此我们可以清楚地看到这一点。然而，这些看似存在的突变大多并非真实存在，因为突变发生的频率随时间推移大致恒定。此外，由于尼安德特人的骨骼年代久远，它们实际上比现代人类基因组更接近共同祖先，因此积累的突变数量应该更少。基于尼安德特人谱系中突变过多的程度，我们估计我们使用过的尼安德特人序列平均每两百个DNA碱基就存在一个错误。虽然这听起来似乎很小，但实际上远高于尼安德特人和现代人之间真实差异的发生率。因此，我们发现的尼安德特人序列和现代人序列之间的大部分差异都是测量过程中产生的误差，而非尼安德特人和现代人基因组之间真正的差异。为了解决这个问题，我们将研究范围限定在已知在现代人类基因组中存在变异的位点。在这些位点上，约0.5%的错误率太低，不会影响结果的解读。基于这些位点，我们设计了一种数学检验方法，用于衡量尼安德特人与某些现代人类的亲缘关系是否比其他现代人类更近。

The Neanderthal genome sequences we were working with were unfortunately full of errors. We could see as much because the data suggested that several times more mutations had occurred on the Neanderthal lineage than on the modern human lineage after the two sequences separated from their common ancestors. Most of these apparent mutations could not be real, since mutations occur at an approximately constant rate over time, and as the Neanderthal bones were ancient, they were actually closer in time to the common ancestor than are present-day human genomes, and so should have accumulated fewer mutations. Based on the degree of excess mutations on the Neanderthal lineage, we estimated that the Neanderthal sequences we were working with had a mistake approximately every two hundred DNA letters. While this might sound small, it is actually much higher than the rate of true differences between Neanderthals and present-day humans, so most of the differences we found between the Neanderthal sequence and present-day human sequences were errors created by the measurement process and not genuine differences between the Neanderthal and present-day human genomes. To deal with the problem, we restricted our study to positions in the genome that are known to be variable among present-day humans. At these positions, an error rate of about 0.5 percent was too low to confuse the interpretation. Based on these positions, we designed a mathematical test for measuring whether Neanderthals were more closely related to some present-day humans than to others.

我们开发的这项测试现在被称为“四群体测试”，它已成为比较不同群体的重要工具。该测试以四个基因组中相同位置的DNA序列作为输入：例如，两个现代人类基因组、尼安德特人和一只黑猩猩的基因组。它检测在两个现代人类基因组中存在差异的突变位点上，是否也存在尼安德特人基因组中观察到的突变——这必然反映的是发生在最终分离之前的突变。尼安德特人和现代人——尼安德特人与现代人群体的匹配率与尼安德特人与现代人群体的匹配率不同。如果这两个现代人群体都源自一个共同的祖先群体，该群体更早地与尼安德特人的祖先群体分离，那么突变在现代人群体中的遗传概率应该没有差异，因此，这两个现代人群体与尼安德特人基因组的匹配率应该相等。相反，如果尼安德特人和一些现代人杂交，那么杂交产生的现代人群体将与尼安德特人共享更多的突变。

The test we developed is now called the “Four Population Test,” and it has become a workhorse for comparing populations. The test takes as its input the DNA letters seen at the same position in four genomes: for example, two modern human genomes, the Neanderthal, and a chimpanzee. It examines whether, at positions where there is a mutation distinguishing the two modern human genomes that is also observed in the Neanderthal genome—which must reflect a mutation that occurred prior to the final separation of Neanderthals and modern humans—the Neanderthal matches the second human population at a different rate from the first. If the two modern humans descend from a common ancestral population that separated earlier from the ancestors of Neanderthals, there is no reason why the mutation is more likely to have been passed down one modern human line than another, and thus the rate of matching of each of the two modern human genomes to Neanderthal is expected to be equal. In contrast, if Neanderthals and some modern humans interbred, the modern human population descended from the interbreeding will share more mutations with Neanderthals.

当我们测试了不同现代人类群体时，我们发现尼安德特人与欧洲人、东亚人和新几内亚人的亲缘关系大致相同，但与所有非非洲人的亲缘关系都比与所有撒哈拉以南非洲人的亲缘关系更近，包括与西非人这样差异很大的群体。以及来自南部非洲的桑人狩猎采集者。虽然差异很小，但这些发现偶然发生的概率不到万亿分之一。无论我们分析数据的方式如何，都得出了这一结论。如果尼安德特人的祖先与非非洲人的祖先杂交，但没有与非洲人的祖先杂交，那么就会出现这种模式。

When we tested diverse present-day human populations, we found Neanderthals to be about equally close to Europeans, East Asians, and New Guineans, but closer to all non-Africans than to all sub-Saharan Africans, including populations as different as West Africans and San hunter-gatherers from southern Africa. The difference was slight, but the probability of these findings happening by chance was less than one in a quadrillion. We reached this conclusion however we analyzed the data. This was the pattern that would be expected if Neanderthals had interbred with the ancestors of non-Africans but not Africans.

试图销毁证据

Trying to Make the Evidence Go Away

我们对这一结论持怀疑态度，因为它与当时的科学共识相悖——而这一共识深深影响了我们团队的许多成员。帕博曾在一家实验室接受博士后训练，该实验室于1987年发现，如今人类线粒体DNA谱系分化最显著的地区位于非洲，这为所有现代人类起源于非洲提供了强有力的证据。帕博本人在1997年的研究进一步强化了人类起源于非洲的观点，他发现尼安德特人的线粒体DNA远远超出了所有现代人类的变异范围。 ¹⁹

We were skeptical about this conclusion because it went against the scientific consensus of the time—a consensus that had been strongly impressed on many members of our team. Pääbo had done his postdoctoral training in the laboratory that in 1987 had discovered that the most deeply splitting human mitochondrial DNA lineages are found today in Africa, providing strong evidence in favor of an African origin for all modern humans. Pääbo’s own 1997 work strengthened the evidence for a purely African origin by showing that Neanderthal mitochondrial DNA fell far outside all modern human variation.¹⁹

我当初加入尼安德特人基因组计划时，也对尼安德特人与现代人类杂交的可能性抱有强烈的偏见。我的博士生导师大卫·戈德斯坦是卢卡·​​卡瓦利-斯福尔扎的学生，后者将“走出非洲”的人类进化模型作为其核心，而我深受这种范式的影响。我所了解的遗传数据如此一致地支持“走出非洲”的观点，以至于在我看来，最严格的“走出非洲”假说——即现代人类的祖先与尼安德特人之间没有杂交——似乎是一个合理的选择。

I too came into the Neanderthal genome project with a strong bias against the possibility of Neanderthal interbreeding with modern humans. My Ph.D. supervisor, David Goldstein, was a student of Luca Cavalli-Sforza, who had made a fully out-of-Africa model a centerpiece of his models of human evolution, and I was steeped in this paradigm. The genetic data I knew about supported the out-of-Africa picture so consistently that from my perspective the strictest possible version of the out-of-Africa hypothesis, in which there was no interbreeding between the ancestors of present-day humans and Neanderthals, seemed like a good bet.

基于这样的背景，我们对所发现的与尼安德特人杂交的证据深表怀疑，因此我们采用了一系列极其严格的检验方法，以找出证据中的漏洞。我们检验了结果是否依赖于我们使用的基因组测序技术，但我们使用两种截然不同的技术都得到了相同的结果。我们曾考虑过，这一发现可能是古代DNA高错误率造成的假象，已知这种错误率对某些DNA碱基的影响远大于其他碱基。然而，无论我们分析的是哪种类型的突变，都得到了相同的结果。我们怀疑，这一发现是否是由于现代人类污染了尼安德特人样本所致。尽管帕博团队在实验室中采取了预防措施，我们也对数据进行了测试以测量现代人类污染程度，结果表明，即使存在污染，其量也太小，不足以产生我们观察到的模式，但这种污染或许仍然会污染数据。然而，即使存在现代人类的污染，我们观察到的模式也与预期截然不同。如果确实存在污染，那么最有可能的来源是欧洲人，因为我们分析的几乎所有尼安德特人骨骼都是由欧洲人挖掘和处理的。然而，我们获得的尼安德特人序列与欧洲人的亲缘关系并不比与东亚人或新几内亚人的亲缘关系更近——这三个人群截然不同。

Coming from this background, we were deeply suspicious of the evidence we were finding for interbreeding with Neanderthals, and so we applied a particularly stringent series of tests in order to find some problem with our evidence. We tested whether the result was dependent on the genome sequencing technology that we used, but we obtained the same result from two very different technologies. We considered the possibility that the finding might be an artifact of a high rate of error in ancient DNA, which is known to affect particular DNA letters much more than others. However, we obtained the same result regardless of the type of mutation we analyzed. We wondered if our finding resulted from contamination of the Neanderthal sample by present-day humans. This could perhaps have tainted the data despite the measures that Pääbo’s team had taken to guard against it in the lab, and despite the tests we had performed on the data to measure the degree of modern human contamination, which had suggested that any contamination that was present was too small to produce the patterns we observed. However, even if there had been contamination from present-day humans, the patterns we observed looked nothing like what would be expected from it. If there had been contamination, it would most likely have come from a European, since almost all the Neanderthal bones we analyzed were excavated and handled by Europeans. Yet the Neanderthal sequence we had was no closer to Europeans than to East Asians or to New Guineans—three very different populations.

我们当时仍持怀疑态度，想知道是否有什么我们未曾想到的因素可以解释这些模式。2009年6月，我参加了密歇根大学举办的一次会议，在那里我遇到了拉斯穆斯·尼尔森（Rasmus Nielsen），他一直在研究来自世界各地不同人群的基因组。在基因组的大部分区域，非洲人的遗传多样性高于非非洲人，并且携带着分化程度最高的谱系，线粒体DNA的情况也是如此。但尼尔森发现，在基因组中存在一些罕见的区域，在这些区域，非非洲人的遗传多样性高于非洲人，这是因为某些谱系很早就从现代人类序列树中分离出来，并且只存在于非非洲人中。这些序列很可能源自与非非洲人杂交的远古人类。尼尔森加入了我们的合作项目，并将他和他的同事们发现的区域与现有数据进行了比较。当他把十二个特殊区域与尼安德特人的基因组序列进行比较时，发现其中十个区域与尼安德特人的序列高度匹配。这个比例太高，不可能是偶然发生的。尼尔森发现的大部分高度分化的DNA片段必然起源于尼安德特人。

We remained skeptical, wondering if something we had not thought of could explain the patterns. Then, in June 2009, I attended a conference at the University of Michigan where I met Rasmus Nielsen, who had been scanning through the genomes of diverse humans from around the world. In most parts of the genome, Africans are more genetically diverse than non-Africans and carry the most deeply diverging lineages, as is the case with mitochondrial DNA. But Nielsen was identifying rare places in the genome where the genetic diversity among non-Africans was greater than in Africans because of lineages that split off the tree of present-day human sequences early and were present only in non-Africans. These sequences just might be derived from archaic humans who had interbred with non-Africans. Nielsen joined our collaboration and compared the regions he and his colleagues identified to the data. When he compared twelve of his special regions to the Neanderthal genome sequence, he found that in ten of them there was a close match to the Neanderthal. This was far too high a fraction to happen by chance. Most of Nielsen’s highly divergent bits of DNA had to be Neanderthal in origin.

接下来，我们确定了尼安德特人相关遗传物质进入非非洲人祖先的时间。为此，我们利用了重组——在精子或卵子生成过程中，亲代DNA片段相互交换，产生新的拼接染色体并遗传给后代。例如，假设一位女性是尼安德特人母亲和现代人父亲的第一代混血儿。在她的细胞中，每一对染色体都由一条完整的尼安德特人染色体和一条完整的现代人染色体组成。然而，她的卵子中含有23条混合染色体。其中一条卵子中的染色体可能前半部分来自尼安德特人，后半部分来自现代人。假设她与一位现代人交配，这种混合遗传会随着更多现代人的后代不断延续。经过数代繁衍，尼安德特人DNA片段被切割成越来越小的片段，重组就像食物处理机的高速刀片一样，在每一代中随机地将亲代DNA拼接到染色体上。通过测量现代人类体内与尼安德特人相关的DNA片段的典型长度，可以明显看出，与尼安德特人基因组匹配的序列长度远大于与撒哈拉以南非洲人匹配的序列长度。通过基因组，我们可以了解自尼安德特人DNA进入现代人祖先以来已经过去了多少代。

Next, we obtained a date for when the Neanderthal-related genetic material entered the ancestors of non-Africans. To do this, we took advantage of recombination—the process that occurs during the production of a person’s sperm or eggs that swaps large segments of parental DNA to produce novel spliced chromosomes that are passed to the offspring. For example, consider a woman who is a first-generation mixture of a Neanderthal mother and a modern human father. In her cells, each pair of her chromosomes consists of one unbroken Neanderthal chromosome and one unbroken modern human chromosome. However, her eggs contain twenty-three mixed chromosomes. One chromosome in an egg of hers might have its first half of Neanderthal origin and its other half of modern human origin. Suppose she mates with a modern human, and mixture continues down the generations with more modern humans. Over the generations, the segments of Neanderthal DNA get chopped into smaller and smaller bits, with recombination operating like the whirring blade of a food processor, splicing the parental DNA at random positions along the chromosome in each generation. By measuring the typical sizes of the stretches of Neanderthal-related DNA in present humans, evident from the size of sequences that match the Neanderthal genome more than they do sub-Saharan African genomes, we can learn how many generations have passed since the Neanderthal DNA entered a modern person’s ancestors.

通过这种方法，我们发现至少有一些与尼安德特人相关的遗传物质在大约8.6万至3.7万年前进入了现代非非洲人的祖先体内。 ²⁰此后，我们通过分析一位来自西伯利亚的现代人的古代DNA，进一步修正了这一时间。放射性碳定年研究表明，这位现代人生活在大约4.5万年前。该个体体内源自尼安德特人的DNA片段平均比现代人体内源自尼安德特人的DNA片段长7倍，这证实他生活在更接近尼安德特人基因混合事件发生的时间。他与基因混合事件发生时间的接近性使得我们能够获得一个更精确的日期：5.4万至4.9万年前。 ²¹

With this approach, we found that at least some Neanderthal-related genetic material came into the ancestors of present-day non-Africans eighty-six thousand to thirty-seven thousand years ago.²⁰ We have since refined this date by analyzing ancient DNA from a modern human from Siberia who, radiocarbon dating studies show, lived around forty-five thousand years ago. The stretches of Neanderthal-derived DNA in this individual are on average seven times larger than the stretches of Neanderthal-derived DNA in modern humans today, confirming that he lived much closer to the time of Neanderthal mixture. His proximity in time to the mixing event makes it possible to obtain a more accurate date of fifty-four thousand to forty-nine thousand years ago.²¹

但在2012年，我们尚未证实我们探测到的杂交现象确实是与尼安德特人本身发生的。最严厉的质疑来自格雷厄姆·库普，他坚信我们探测到的是与古人类的杂交，但他指出，这种杂交可能并非真的发生在尼安德特人身上。 ²² 相反，这些模式可能是杂交的结果。而这种古人类目前尚不为人知，它与尼安德特人有远亲关系。

But in 2012 we hadn’t yet proven that the interbreeding we had detected was with Neanderthals themselves. The most serious questioning came from Graham Coop, who was convinced that we had detected interbreeding with archaic humans, but pointed out that it was possible that the interbreeding hadn’t actually been with Neanderthals.²² Instead, the patterns could be the result of interbreeding with an as yet unknown archaic human in turn distantly related to Neanderthals.

一年后，帕博的实验室对一块发现于西伯利亚南部、距今至少五万年的脚趾骨中的高质量尼安德特人基因组进行了测序（如果样本的年代超过五万年，放射性碳定年法只能提供最低年代，因此实际年代可能更久远），从而排除了库普的假设。 ²³对于这个基因组，我们收集到的数据量大约是克罗地亚尼安德特人的四十倍。有了如此庞大的数据量，我们可以交叉验证序列并修正错误。最终得到的序列比大多数现代人类基因组的错误率更低。高质量的序列使我们能够根据自现代人类和尼安德特人分化以来谱系中发生的突变数量，来确定二者之间的亲缘关系。我们发现，在过去五十万年中，西伯利亚尼安德特人与现代撒哈拉以南非洲人几乎没有共同祖先的基因片段。然而，在过去大约十万年的时间里，他们与非非洲人群存在基因片段共享。这些时间点与尼安德特人在西欧亚大陆完全定居的时间范围相吻合。这意味着，杂交的对象是真正的尼安德特人，而不是某些远亲群体。

A year later we were able to rule out Coop’s scenario after Pääbo’s laboratory sequenced a high-quality Neanderthal genome from a toe bone found in southern Siberia dating to at least fifty thousand years ago (if a sample is older than about fifty thousand years, radiocarbon dating can only provide a minimum date, so it actually could be substantially older).²³ For this genome, we were able to gather about forty times more data than from the Croatian Neanderthal. With so much data, we could cross-check the sequence and edit away the errors. The resulting sequence was freer of errors than most genomes that are generated from living humans. The high-quality sequence allowed us to determine how closely related modern humans and Neanderthals are to each other based on the number of mutations that have occurred on the lineages since they separated. We found few or no segments where the Siberian Neanderthal shared common ancestors with present-day sub-Saharan Africans within the last half million years. However, there were shared segments with non-Africans roughly within the past one hundred thousand years. These dates fell within the time frame when Neanderthals were fully established in West Eurasia. This meant that the interbreeding was with true Neanderthals, not some distantly related groups.

近东地区的混合

Mixing in the Near East

那么，如今非洲以外的人们究竟拥有多少尼安德特人血统呢？我们发现，如今非非洲人群的基因组中约有1.5%至2.1%源自尼安德特人，²⁴其中东亚人的含量较高，欧洲人的含量较低，尽管欧洲才是尼安德特人的故乡。25^我们现在知道，至少部分原因在于基因稀释。来自9000年前欧洲人的古DNA显示，农业出现之前的欧洲人与今天的东亚人一样，都拥有相当比例的尼安德特人血统。26^现代欧洲人尼安德特人血统的减少，是因为他们体内还含有一些其他族裔的基因。他们的祖先来自一群在与尼安德特人混血之前就与其他所有非非洲人分离的人群（本书第二部分将讲述古代DNA揭示的这群早期分离人群的故事）。携带这种血统的农民的扩散稀释了欧洲的尼安德特人血统，但在东亚则没有^。27

So how much Neanderthal ancestry do people outside of Africa carry today? We found that non-African genomes today are around 1.5 to 2.1 percent Neanderthal in origin,²⁴ with the higher numbers in East Asians and the lower numbers in Europeans, despite the fact that Europe was the homeland of the Neanderthals.²⁵ We now know that at least part of the explanation is dilution. Ancient DNA from Europeans who lived before nine thousand years ago shows that pre-farming Europeans had just as much Neanderthal ancestry as East Asians do today.²⁶ The reduction in Neanderthal ancestry in present-day Europeans is due to the fact that they harbor some of their ancestry from a group of people who separated from all other non-Africans prior to the mixture with Neanderthals (the story of this early-splitting group revealed by ancient DNA is told in part II of this book). The spread of farmers with this inheritance diluted the Neanderthal ancestry in Europe, but not in East Asia.²⁷

仅从考古证据来看，人们很容易推测尼安德特人与现代人类在欧洲——尼安德特人的起源地——发生了杂交。但是，这是否就是对现代人类影响最深远的杂交事件发生的地点呢？基因数据无法给出确切答案。基因数据可以显示人类之间的亲缘关系，但人类一生中即使步行也能迁徙数千公里，因此基因模式未必反映的是携带该基因的人群居住地附近发生的事件。如果说近几年的古代DNA研究揭示了什么，那就是现代人类的地理分布往往无法准确反映其祖先的居住地。

Based on archaeological evidence alone, it would seem a natural guess that Neanderthals interbred with modern humans in Europe, the place where Neanderthals originated. But is that the place where the main interbreeding that left its mark in people today occurred? The genetic data cannot tell us for sure. Genetic data can show how people are related, but humans are capable of migrating thousands of kilometers in a lifetime even on foot, so genetic patterns need not reflect events that occurred near the locations where the people who carry the DNA live. If the ancient DNA studies of the last few years have shown anything clearly, it is that the geographic distribution of people living today is often misleading about the dwelling places of their ancestors.

然而，我们可以对地理起源做出一些合理的推测。如今，不仅在欧洲人身上，在东亚人和新几内亚人身上也发现了通婚的证据。欧洲在欧亚大陆上就像一个死胡同，不太可能是现代人类向东扩张的必经之路。那么，尼安德特人和现代人类究竟在哪里相遇并融合，从而繁衍出一个不仅扩张到欧洲，还扩展到东亚和新几内亚的族群呢？考古学家已经证明，在近东地区，尼安德特人和现代人类在13万至5万年前至少两次交替占据主导地位，因此我们有理由推测他们可能在此期间相遇。所以，近东地区的通婚为欧洲人和东亚人共同拥有的尼安德特人血统提供了一个合理的解释。

However, we can make plausible conjectures about geographic origin. Evidence of interbreeding is detected today not just in Europeans but also in East Asians and New Guineans. Europe is a cul-de-sac of sorts within Eurasia, and would not have been a likely detour for modern humans expanding eastward. So where could Neanderthals and modern humans have met and mixed to give rise to a population that expanded not only to Europe but also to East Asia and New Guinea? Archaeologists have shown how in the Near East, Neanderthals and modern humans traded places as the dominant human population at least twice between 130,000 and 50,000 years ago, and it is reasonable to guess that they might have met during this period. So interbreeding in the Near East provides a plausible explanation for the Neanderthal ancestry that is shared by Europeans and East Asians.

欧洲是否发生过杂交？2014年，帕博的研究小组对罗马尼亚奥阿塞洞穴出土的一具骨骼进行了DNA测序。这具骨骼正是埃里克·特林考斯根据其头骨特征（该特征与尼安德特人和现代人相似）而推断为尼安德特人和现代人杂交的个体。 ²⁸我们对数据的分析表明，奥阿塞洞穴的这名个体（放射性碳测年研究表明其生活在约公元前1500年）四万年前，奥阿塞人拥有约6%至9%的尼安德特人血统，远高于我们今天在非非洲裔人群中测得的约2%。 ²⁹某些尼安德特人DNA片段延伸至其染色体长度的三分之一——如此之长且未受重组破坏，我们可以确定，奥阿塞人的家族谱系中，其祖先中至少有六代人是真正的尼安德特人。污染无法解释这些发现，因为污染会稀释奥阿塞人体内的尼安德特人血统，而不是增加。污染还会导致基因组中出现与尼安德特人随机匹配的情况，而不是像现在这样，只需在基因组上绘制出与尼安德特人基因组序列匹配度高于与现代人类匹配度的突变位置，就能轻易识别出大段的尼安德特人DNA。这种尼安德特人杂交的证据无需统计数据，证据就摆在那里。

Did interbreeding happen in Europe at all? In 2014, Pääbo’s group sequenced DNA from a skeleton from Oase Cave in Romania, the same skeleton that Erik Trinkaus had interpreted as a hybrid of Neanderthals with modern humans, based on features of its skull that were similar to both.²⁸ Our analysis of the data showed that the Oase individual, who radiocarbon dating studies had shown lived about forty thousand years ago, had around 6 to 9 percent Neanderthal ancestry, far more than the approximately 2 percent that we measure in present-day non-Africans.²⁹ Some stretches of Neanderthal DNA extend a third of the length of his chromosomes—a span so large and unbroken by recombination that we can be sure that the Oase individual had an actual Neanderthal no more than six generations back in his family tree. Contamination cannot explain these findings, as it would dilute the Neanderthal ancestry in the Oase individual, not increase it. It would also generate random matching to Neanderthals throughout the genome, not large stretches of Neanderthal DNA that could be readily identified by eye when we simply plotted along the genome the positions of mutations that match the Neanderthal genome sequence more closely than they match modern humans. This evidence of Neanderthal interbreeding didn’t need statistics. The proof was in the picture.

最近对奥阿塞个体家谱的研究表明，现代人类和尼安德特人也曾在尼安德特人的故乡——欧洲——发生过杂交。但奥阿塞所属的那个群体——尽管带有与欧洲尼安德特人明显杂交的印记——可能并未在当今人群中留下任何后代。我们分析了奥阿塞的基因组，并未发现任何证据表明他与欧洲人的亲缘关系比与东亚人的亲缘关系更近。这意味着他必定属于一个进化上的死胡同——一个早期抵达欧洲的现代人类先驱群体，他们在那里短暂繁衍并与当地的尼安德特人杂交，之后便灭绝了。因此，虽然奥阿塞个体为尼安德特人和现代人类在欧洲发生过杂交提供了强有力的证据，但他并不能证明当今非非洲人群的尼安德特人血统源自欧洲尼安德特人。目前来看，非非洲人中最有可能的尼安德特人祖先来源是近东尼安德特人。

The discoveries about the interbreeding in the recent family tree of the Oase individual suggested that modern humans and Neanderthals also hybridized in Europe, the homeland of the Neanderthals. But the population of which Oase was a part—and which carried this clear imprint of interbreeding with European Neanderthals—may not have left any descendants among people living today. When we analyzed the genome of Oase, we found no evidence that he was more closely related to Europeans than to East Asians. This means that he had to have been part of a population that was an evolutionary dead end—a pioneer modern human population that arrived early in Europe, flourished there briefly and interbred with local Neanderthals, and then went extinct. Thus, while the Oase individual provides powerful evidence that interbreeding between Neanderthals and modern humans occurred in Europe, he does not provide any evidence that Neanderthal ancestry in non-Africans today is derived from European Neanderthals. It remains the case that the most likely source of Neanderthal ancestry in non-Africans is Near Eastern Neanderthals.

奥阿塞属于一个已灭绝的族群这一发现，与欧洲第一批现代人类的考古记录相符。这些人制造的石器种类繁多，但与奥阿塞所在的族群一样，大多数都已灭绝。某种意义上说，这些文化在几千年后就从考古记录中消失了。然而，一种被称为原始奥瑞纳文化的风格——据信源自近东更早的阿赫马尔文化——在三万九千年后仍然存在，并可能发展成为奥瑞纳文化，即欧洲第一个广泛传播的现代人类文化。 ³⁰如果奥瑞纳文化工具的制造者与其他早期现代人类（如奥阿塞人）的迁徙路线不同，那么这些模式就可以得到解释。这种假设可以解释为什么奥阿塞人与欧洲当地的尼安德特人大量通婚，而如今欧洲人的尼安德特人血统却并非来自欧洲。

The finding that Oase was from a dead-end population accords with the archaeological record of the first modern humans of Europe. The stone tools these humans made came in a variety of styles, but like the population of Oase himself, most were dead ends in the sense that they disappeared from the archaeological record after a few thousand years. However, one style known as the Protoaurignacian—thought to derive from the earlier Ahmarian of the Near East—persisted after thirty-nine thousand years ago and likely developed into the Aurignacian, the first widespread modern human culture in Europe.³⁰ These patterns could be explained if the makers of Aurignacian tools derived from a different migration into Europe compared to other early modern humans like Oase. This scenario could explain how it could be that Oase’s population interbred heavily with local European Neanderthals, and yet the Neanderthal ancestry in Europeans today is not from Europe.

处于兼容性边缘的两组人群

Two Groups at the Edge of Compatibility

杂交后代的低生育率也可能导致现代人DNA中尼安德特人血统比例降低。洛朗·埃斯科菲耶(Laurent Excoffier)最早提出了这种可能性。他通过对动植物的研究发现，当一个种群迁徙到另一个可以与之杂交的种群所居住的地区时，即使杂交率很低，也足以在后代中产生高比例的混合血统——远高于如今非非洲裔人群中约2%的尼安德特人血统。埃斯科菲耶认为，现代人类基因组中尼安德特人血统比例如此之低的唯一解释是，不断扩张的现代人类与其他现代人类交配的后代的生育率至少是与生活在他们中间的尼安德特人交配的五十倍。 ³¹他认为，最可能的解释是，尼安德特人和现代人类的后代的生育率远低于现代人类之间交配的后代。

The low fertility of hybrids may also have reduced Neanderthal ancestry in the DNA of people living today. This possibility was first advanced by Laurent Excoffier, who knew from studies of animals and plants that when one population moves into a region occupied by another population with which it can interbreed, even a small rate of interbreeding is enough to produce high proportions of mixture in the descendants—far more than the approximately 2 percent Neanderthal ancestry seen in non-Africans today. Excoffier argued that the only way that the modern human genome could have ended up with so little Neanderthal ancestry was if expanding modern humans had offspring with other modern humans at least fifty times more often than they did with the Neanderthals living in their midst.³¹ He thought that the most likely explanation for this was that Neanderthals and modern human offspring were much less fertile than the offspring of matings between pairs of modern humans.

我并不认同这种说法。比起低杂交生育率，我更倾向于认为，由于社会原因，当时人类之间通婚很少。即使在今天，许多现代人类群体也因为文化、宗教或阶级壁垒而保持相对封闭的状态。那么，现代人类和尼安德特人相遇时，又怎会例外呢？

I wasn’t convinced by this argument. Rather than low hybrid fertility, I favored the explanation that there simply wasn’t much interbreeding for social reasons. Even today, many groups of modern humans keep largely to themselves because of cultural, religious, or caste barriers. Why should it have been any different for modern humans and Neanderthals when they encountered one another?

但埃克斯科菲尔的发现确实有其重要之处。当我们和其他研究人员分析进入现代人类群体的尼安德特人DNA片段，并绘制出它们在基因组中的位置时，这一点变得显而易见。为了实现这一目标，我实验室的斯里拉姆·桑卡拉拉曼（Sriram Sankararaman）寻找那些在已测序的尼安德特人基因组中存在，但在撒哈拉以南非洲人中罕见或缺失的突变。通过研究这些突变片段，我们能够在每个非非洲人基因组中找到相当一部分尼安德特人祖先片段。通过观察这些尼安德特人祖先片段在基因组中的位置，我们发现尼安德特人杂交对当今非非洲人基因组的影响差异巨大。非非洲人群中尼安德特人祖先的平均比例约为2%，但分布并不均匀。在超过一半的基因组中，我们没有检测到任何尼安德特人祖先。但在基因组的某些特殊区域，超过50%的DNA序列来自尼安德特人。 ³²

But Excoffier got something important right. This became evident when we and others analyzed the bits of Neanderthal DNA that entered into the modern human population and mapped their positions in the genome. To do this, Sriram Sankararaman in my laboratory searched for mutations that were present in the sequenced Neanderthals but were rare or absent in sub-Saharan Africans. By studying stretches of such mutations, we were able to find a substantial fraction of all the Neanderthal ancestry fragments in each non-African. Looking at where in the genome these Neanderthal ancestry fragments occurred, it became clear that the impact of Neanderthal interbreeding varied dramatically across the genome of non-African people today. The average proportion of Neanderthal ancestry in non-African populations is around 2 percent, but it is not spread evenly. In more than half the genome, no Neanderthal ancestry has been detected in anyone. But in some unusual places in the genome, more than 50 percent of DNA sequences are from Neanderthals.³²

帮助我们理解这种模式形成的关键线索来自对非非洲人群基因组中尼安德特人血统稀少区域的分析。在任何一段DNA中，人群中尼安德特人血统的缺失都可能是偶然发生的，正如我们认为线粒体DNA的情况一样。然而，除非自然选择系统性地清除，否则基因组中具有特定生物学功能的相当一部分区域不太可能系统性地失去尼安德特人血统。

A critical clue that helped us to understand how this pattern had formed came from studying the places in non-African genomes where Neanderthal ancestry is rare. In any one stretch of DNA, an absence of Neanderthal ancestry in the population can happen by chance, as we think is the case for mitochondrial DNA. However, it is improbable that a substantial subset of the genome with particular biological functions will be systematically depleted of Neanderthal ancestry unless natural selection systematically worked to remove it.

但我们发现的证据恰恰证明了尼安德特人血统被系统性地清除——而且，令人惊讶的是，我们发现，在已知与杂交后代生育能力相关的基因组的两个部分中，尼安德特人血统通过自然选择被特别强烈地消耗掉了。

But evidence of systematic removal of Neanderthal ancestry is exactly what we found—and, remarkably, we found a particularly intense depletion of Neanderthal ancestry by natural selection in two parts of the genome known to be relevant to the fertility of hybrids.

尼安德特人血统减少的第一个位置在X染色体上，X染色体是两条性染色体之一。这让我想起了我和尼克·帕特森（Nick Patterson）在几年前共同开展并发表的一项关于人类和黑猩猩祖先分离的研究中遇到的一个模式。33^在任何人群中，每四条其他染色体中只有三条X染色体（因为女性携带两条，男性只携带一条），与大多数其他染色体在两性中各有两个拷贝的情况相反）。这意味着在任何一代中，任意两个X染色体拥有共同祖先的概率是其他染色体中任意两个拥有共同祖先的概率的三分之四。由此可知，任意一对X染色体序列源自共同祖先序列的预期时间约为基因组其他部分所需时间的三分之四。然而，实际数据表明，这个数字大约只有一半甚至更少。 ³⁴在我们对人类和黑猩猩共同祖先群体的研究中，我们未能找到任何可以解释这种模式的历史因素，例如雌性在不同群体间迁徙的频率低于雄性，或者雌性生育子女的数量比雄性更不稳定，又或者种群的扩张或收缩。然而，这种模式可以用这样一种历史来解释：人类和黑猩猩的祖先最初是分开的，然后结合在一起，形成了人类或黑猩猩的祖先，之后这两个谱系才最终分离。

The first place of reduced Neanderthal ancestry was on chromosome X, one of the two sex chromosomes. This reminded me of a pattern that Nick Patterson and I had run into in our work on the separation of human and chimpanzee ancestors in a study we had carried out together and published years before.³³ There are only three copies of chromosome X in any population for every four other chromosomes (because females carry two copies and males only one, in contrast to two copies in each sex for most of the rest of the chromosomes). This means that in any one generation, the probability that any two X chromosomes share a common parent is four-thirds the probability that any two of one of the other chromosomes share a common parent. It follows that the expected time since any pair of X chromosome sequences descend from a common ancestral sequence is about four-thirds of that in the rest of the genome. In fact, though, the real data suggest a number that is around half or even less.³⁴ In our study of the common ancestral population of humans and chimpanzees, we had not been able to identify any history that could explain this pattern, such as a lower rate of females moving among groups than males, or a more variable number of children in females than in males, or population expansion or contraction. However, the patterns could be explained by a history in which the ancestors of humans and chimpanzees initially separated, then came together to form either human or chimpanzee ancestors before the final separation of the two lineages.

为什么杂交会导致X染色体上的遗传变异远低于基因组其他部分的变异？对动物界多种物种的研究表明，当两个种群分离足够长的时间后，杂交后代的生育力会降低。在像我们这样的哺乳动物中，雄性生育力降低的情况更为常见，而导致生育力降低的遗传因素集中在X染色体上。^因此，当两个种群分离到后代生育力降低的程度，但仍然杂交产生杂交后代时，自然选择必然会强烈地去除导致生育力降低的因素。由于导致不育的基因集中在X染色体上，这一过程在X染色体上尤为明显。结果，X染色体上的DNA片段往往会受到自然选择的影响，这些片段来自为杂交种群提供大部分祖先基因的种群。这导致杂交种群的 X 染色体几乎完全来自多数种群，从而导致杂交种群与其中一个杂交种群之间 X 染色体的遗传分化异常低，这与人类和黑猩猩的模式一致。

How is it that hybridization can lead to so much less genetic variation on chromosome X than on the rest of the genome? From studies of a variety of species across the animal kingdom, it is known that when two populations are separated for long enough, hybrid offspring have reduced fertility. In mammals like us, reduced fertility is much more common in males, and the genetic factors contributing to this reduced fertility are concentrated on chromosome X.³⁵ So when two populations are so separated that their offspring have reduced fertility, but nevertheless mix together to produce hybrids, it is expected that there will be intense natural selection to remove the factors contributing to reduced fertility. This process will be especially evident on chromosome X because of the concentration of genes contributing to infertility on it. As a result, there tends to be natural selection on chromosome X for stretches of DNA from the population that contributed most of the hybrid population’s ancestry. This causes the hybrid population to derive its chromosome X almost entirely from the majority population, leading to an anomalously low genetic divergence on chromosome X between the hybrid population and one of the hybridizing populations, consistent with the pattern seen in humans and chimpanzees.

这种理论预测听起来或许有些异想天开，但实际上在西欧和东欧家鼠杂交种身上得到了证实。这些杂交种分布在一条南北走向的中欧地带，大致沿着冷战时期的铁幕线。虽然由于杂交种不仅携带西欧家鼠的DNA，还携带高度分化的东欧家鼠的DNA，导致其基因组大部分区域的突变密度很高，但X染色体上的突变密度却低得多，因为杂交种几乎不携带东欧种群的DNA，而已知东欧种群的X染色体会导致雄性杂交种不育。 ³⁶

This theoretical prediction might sound fanciful, but in fact it is borne out in hybrids of the western European and eastern European house mouse species in a band of territory that runs in a north-to-south direction through central Europe, roughly along the line of the former Cold War Iron Curtain. While the density of mutations separating the hybrid mice from western European mice is high in most of the genome because the hybrid mice carry DNA not just from western European mice but also from highly divergent eastern European mice, the density on the X chromosome is far less because the hybrid mice harbor very little DNA from the eastern European population whose X chromosomes are known to cause infertility in male hybrids.³⁶

自2006年我们发表论文提出人类或黑猩猩可能起源于一次远古时期的大规模杂交以来，关于人类和黑猩猩祖先中存在远古时期大规模杂交的证据，不仅没有减少，反而更加有力。2012年，Mikkel Schierup、Thomas Mailund及其同事开发了一种新方法，利用遗传数据估算两个现代物种祖先分离的突然性，该方法基于与第一章中描述的Li和Durbin方法类似的原理。³⁷当他们运用该方法研究普通黑猩猩及其远亲倭黑猩猩的分离时间时，他们发现分离非常突然，这与物种被一条在100万至200万年前突然形成的大河（刚果河）分隔的假说相符。相比之下，当他们运用该方法研究人类和黑猩猩时，他们发现种群分化开始后存在一段较长的基因交流期，这与杂交的预期相符。 ³⁸

Since the publication of our paper in 2006 suggesting that either humans or chimpanzees may derive from an ancient major hybridization, the evidence for ancient major hybridization in the ancestry of humans and chimpanzees has, if anything, become even stronger. In 2012 Mikkel Schierup, Thomas Mailund, and colleagues developed a new method to estimate the suddenness of separation of the ancestors of two present-day species from genetic data, based on principles similar to the Li and Durbin approach described in chapter one.³⁷ When they applied the method to study the separation time of common chimpanzees and their distant cousins, bonobos, they found evidence that the separation was very sudden, consistent with the hypothesis that the species were separated by a huge river (the Congo) that formed rather suddenly one to two million years ago. In contrast, when they applied the method to study humans and chimpanzees, they found evidence for an extended period of genetic interchange after population differentiation began, as expected for hybridization.³⁸

更重要的证据来自Schierup和Mailund于2015年发表的一篇论文。他们与其他同事合作，证明非非洲人群X染色体上尼安德特人基因混合缺失的区域，在很大程度上与导致人类和黑猩猩之间遗传分化程度较低的区域相同。 ³⁹如果导致杂交个体生育力下降的突变不仅仅集中在X染色体上，那么这种情况就符合预期。X染色体上的特定区域，尤其是某些特定区域，导致携带尼安德特人血统的男性杂交后代，通过自然选择而被淘汰。这种从X染色体上清除尼安德特人DNA的选择证据，是男性杂交后代生育能力下降的有力证明。

An even more important piece of evidence came from a paper Schierup and Mailund published in 2015, when together with other colleagues, they showed that the regions that are denuded of Neanderthal mixture on chromosome X in non-Africans are to a large extent the same regions that are driving the low genetic divergence between humans and chimpanzees.³⁹ This is what would be expected if mutations that contribute to reduced fertility when they occur in a hybrid individual tend to be concentrated not just on chromosome X, but in particular regions along chromosome X, causing the minority ancestry to be removed from the population by natural selection against the male hybrids who carry it. The evidence of selection to remove Neanderthal DNA from chromosome X was a tell-tale sign that male hybrids had reduced fertility.

我们还发现了尼安德特人和现代人混血后代不育的第二条证据——这条证据与X染色体无关。当混血男性出现生育力下降时，导致生育力下降的基因往往在男性生殖组织中高度活跃，从而导致精子功能障碍。因此，在我向进化生物学家戴文·普雷斯格雷夫斯（Daven Presgraves）展示了X染色体证据后，他向我提出了一个关于男性混血不育假说的预测：在男性睾丸生殖细胞中异常活跃的基因，其尼安德特人祖先成分平均而言会低于在其他身体组织中最活跃的基因。当我们查看真实数据时，普雷斯格雷夫斯的预测得到了完全证实。 ⁴⁰

We also found a second line of evidence for infertility in hybrids of Neanderthals and modern humans—a line of evidence that had nothing to do with the X chromosome. When reduced fertility is observed in hybrid males, the genes responsible tend to be highly active in the male reproductive tissue, causing malfunctions of sperm. So a prediction of the hypothesis of male hybrid infertility suggested to me by evolutionary biologist Daven Presgraves after I showed him the X chromosome evidence is that genes unusually active in the germ cells of a man’s testicles will have less Neanderthal ancestry on average than genes that are most active in other body tissues. When we looked in real data, Presgraves’s prediction was exactly borne out.⁴⁰

现代人类（尤其是那些拥有尼安德特人血统的人类）面临的问题不仅仅是生育能力下降，事实证明，尼安德特人血统不仅在 X 染色体上以及与男性生殖相关的基因周围减少，而且在绝大多数基因周围也减少（“垃圾”基因中含有更多的尼安德特人血统）。基因组中生物学功能较少的部分）。最确凿的证据来自2016年的一项研究，我们在该研究中发表了一个涵盖过去四万五千年间五十多个欧亚人群的全基因组古代DNA数据集。 ⁴¹我们发现，在我们分析的大多数样本中，尼安德特人血统的比例从早期的3%到6%持续下降到后期的约2%，而这一下降是由针对尼安德特人DNA的广泛自然选择所驱动的。

The problems faced by modern humans with Neanderthal ancestry went beyond reduced fertility, as it turns out that Neanderthal ancestry is not just reduced on the X chromosome and around genes important in male reproduction, but is also reduced around the great majority of genes (there is far more Neanderthal ancestry in “junk” parts of the genome with few biological functions). The clearest evidence for this came from a study in 2016, in which we published a genome-wide ancient DNA dataset from more than fifty Eurasians spread over the last forty-five thousand years.⁴¹ We showed that Neanderthal ancestry decreased continually from 3 to 6 percent in most of the samples we analyzed from earlier times to its present-day value of around 2 percent at later times and that this was driven by widespread natural selection against Neanderthal DNA.

尼安德特人活动范围的大部分位于冰河时期导致其赖以生存的动植物种群周期性崩溃的地区，而生活在热带非洲的现代人类祖先可能并未受到同样程度的影响。尼安德特人的基因组多样性约为现代人类的四分之一，这一事实也证实了尼安德特人的种群规模小于现代人类。种群规模较小不利于其遗传健康，因为每一代发生的突变频率波动幅度很大，足以使一些突变在种群中传播，即使面对自然选择通常会降低突变频率的普遍趋势。因此，自尼安德特人和现代人类分离后的^五十万年间，尼安德特人的基因组积累了突变，这些突变在后来的尼安德特人与现代人类杂交时被证明是有害的。

A large part of the Neanderthal range was in a region where ice ages caused periodic collapses of the animal and plant populations that Neanderthals depended on, a problem that may not have afflicted modern human ancestors in tropical Africa to the same extent. There is genetic confirmation for smaller Neanderthal than modern human population sizes from the fact that the diversity of their genomes was about four times smaller. A history of small size is problematic for the genetic health of a population, because the fluctuations in mutation frequency that occur every generation are substantial enough to allow some mutations to spread through the population even in the face of the prevailing wind of natural selection that tends to reduce their frequencies.⁴² So in the half million years since Neanderthals and modern humans separated, Neanderthal genomes accumulated mutations that would prove detrimental when later, Neanderthal/modern human interbreeding occurred.

尼安德特人基因组中存在的问题突变与近期不同现代人类群体混合的情况形成鲜明对比，后者并未发现此类影响的证据。例如，在对约三万名非裔美国人的研究中，我们没有发现任何针对非洲或欧洲血统的自然选择的证据。 ⁴³对此的一种解释是，尼安德特人和现代人类混合时，他们的分离时间大约是西非人和欧洲人分离时间的十倍，这使得生物学上的不相容性有更多的时间发展。另一种解释与对许多物种的研究观察有关，即当群体间出现不育现象时，通常是由于基因组不同区域的两个基因之间的相互作用造成的。由于需要两个基因改变才能产生这种不相容性，因此不育率会随着群体分离时间的平方而增加，所以一个规模是现在十倍的群体分离后，不育率也会随之增加。这意味着基因不相容性增加了一百倍。鉴于此，现代人类杂交后代普遍不育或许就不那么令人惊讶了。

The problematic mutations in the Neanderthal genome form a sharp contrast with more recent mixtures of divergent modern human populations where there is no evidence for such effects. For example, among African Americans, in studies of about thirty thousand people, we have found no evidence for natural selection against African or European ancestry.⁴³ One explanation for this is that when Neanderthals and modern humans mixed they had been separated for about ten times longer than had West Africans and Europeans, giving that much more time for biological incompatibilities to develop. A second explanation relates to the observation, from studies of many species, that when infertility arises between populations, it is often due to interactions between two genes in different parts of the genome. Since two changes are required to produce such an incompatibility, the rate of infertility increases with the square of population separation time, so a ten-times-larger population separation translates to one hundred times more genetic incompatibility. In light of this the lack of infertility in hybrids of present-day humans may no longer seem so surprising.

正题、反题、合题

Thesis, Antithesis, Synthesis

自十八世纪起，欧洲大陆哲学的一个重要脉络认为，思想的演进遵循“辩证法”：对立观点的碰撞最终导向综合。⁴⁴辩证法始于“正题”，随后是“反题”。进步是通过超越引发它的双向辩论的解决之道，即“综合”来实现的。

An important strand in continental European philosophy beginning in the eighteenth century was that the march of ideas proceeds in a “dialectic”: a clash of opposed perspectives that leads to a synthesis.⁴⁴ The dialectic begins with a “thesis,” followed by an “antithesis.” Progress is achieved through a resolution, or “synthesis,” which transcends the two-sided debate that engendered it.

我们对现代人类起源的理解也经历了类似的过程。长期以来，许多人类学家倾向于多区域起源论，即认为世界任何特定地区的现代人类都主要源自生活在同一地理区域的古人类。因此，人们认为欧洲人的祖先很大一部分来自尼安德特人，东亚人的祖先来自一百多万年前迁徙到欧亚大陆东部的古人类，而非洲人的祖先则来自非洲的古人类。这样看来，现代人类群体之间的生物学差异有着极其深远的根源。

So it has been with our understanding of modern human origins. For a long time, many anthropologists favored multiregionalism, the theory that modern humans in any given place in the world descend substantially from archaic humans who lived in the same geographical region. Thus Europeans were thought to derive large proportions of their ancestry from Neanderthals, East Asians from humans who dispersed to eastern Eurasia more than a million years ago, and Africans from African archaic forms. The biological differences among modern human populations would then have extremely deep roots.

多区域起源论很快就遇到了它的对立面——非洲起源论。该理论认为，现代人类并非在世界各地分别从当地的古老物种演化而来，而是起源于大约五万年前从非洲和近东地区开始的一次相对较近的迁徙。“线粒体夏娃”的出现时间较近，而尼安德特人的线粒体DNA则存在着显著的分化，这为该理论提供了最有力的证据。与多区域起源论相反，非洲起源论强调现代人类群体间差异的起源时间较近，而人类骨骼记录的时间跨度却长达数百万年。

Multiregionalism soon encountered its antithesis, the out-of-Africa theory. In this theory, modern humans did not evolve in each location in the world separately from local archaic forms. Instead, modern humans everywhere derive from a relatively recent migration from Africa and the Near East beginning around fifty thousand years ago. The recent date of “Mitochondrial Eve” compared with the deep divergence of Neanderthal mitochondrial DNA provided some of the best evidence for this theory. In opposition to the multiregional hypothesis, the out-of-Africa theory emphasizes the recent origin of the differences among present-day human populations, relative to the multimillion-year time depth of the human skeletal record.

然而，“走出非洲”论也并非完全正确。如今，基于古代DNA研究发现尼安德特人和现代人类之间存在基因交流，我们有了新的综合理论。这印证了“主要起源于非洲”的理论，同时也揭示了那些与尼安德特人有过密切接触的现代人类文化中一些深刻的内涵。虽然基因数据清楚地表明，非洲以外的现代人类起源于一个席卷全球的非洲起源群体的扩张，但我们现在知道，他们之间也发生过一些基因交流。这必然会让我们重新思考我们的祖先以及他们遇到的古人类。尼安德特人比我们想象的更像我们，他们或许具备许多我们通常认为只有现代人类才有的行为。这种融合必然伴随着文化交流——威廉·戈尔丁和简·奥尔的小说恰如其分地描绘了这些相遇。我们还知道，尼安德特人给非非洲人留下了生物学遗产，包括适应欧亚大陆不同环境的基因，我将在下一章中再次探讨这个话题。

Yet the out-of-Africa argument is not entirely right either. We now have a synthesis, driven by the finding of gene flow between Neanderthals and modern humans based on ancient DNA. This affirms a “mostly out-of-Africa” theory, and also reveals something profound about the culture of those modern humans who must have known Neanderthals intimately. While it is clear from the genetic data that modern humans outside of Africa descend from the expansion of an African-origin group that swept around the world, we now know that some interbreeding occurred. This must make us think differently about our ancestors and the archaic humans they encountered. The Neanderthals were more like us than we had imagined, perhaps capable of many behaviors that we typically associate with modern humans. There must have been cultural exchange that accompanied the mixture—the novels by William Golding and Jean Auel were right to dramatize these encounters. We also know that there has been a biological legacy bequeathed by Neanderthals to non-Africans, including genes for adapting to different Eurasian environments, a topic to which I will return in the next chapter.

尼安德特人基因组计划结束后，我仍然对我们遇到的种种惊喜感到震惊。虽然我们发现了尼安德特人和现代人杂交的首个证据，但我仍会担心这或许是个错误。然而，数据却无比一致：尼安德特人杂交的证据无处不在。随着我们继续开展基因研究，我们不断发现越来越多的模式，这些模式反映了这种杂交对现代人类基因组产生的巨大影响。

At the conclusion of the Neanderthal genome project, I am still amazed by the surprises we encountered. Having found the first evidence of interbreeding between Neanderthals and modern humans, I continue to have nightmares that the finding is some kind of mistake. But the data are sternly consistent: the evidence for Neanderthal interbreeding turns out to be everywhere. As we continue to do genetic work, we keep encountering more and more patterns that reflect the extraordinary impact this interbreeding has had on the genomes of people living today.

因此，基因记录迫使我们做出抉择。它非但没有证实科学家的预期，反而带来了意想不到的发现。我们现在知道，尼安德特人和现代人的混血种群曾生活在欧洲和整个欧亚大陆，虽然许多混血种群最终灭绝，但有些存活了下来，并繁衍出了如今庞大的人口。我们现在大致知道了现代人和尼安德特人的谱系何时分离。我们也知道，当这些谱系再次相遇时，它们已经进化到生物学兼容性的极限。这就引出了一个问题：尼安德特人是唯一与我们的祖先杂交的古人类吗？或者，在我们过去的历史上还发生过其他大规模的杂交事件？

So the genetic record has forced our hand. Instead of confirming scientists’ expectations, it has produced surprises. We now know that Neanderthal/modern human hybrid populations were living in Europe and across Eurasia, and that while many hybrid populations eventually died out, some survived and gave rise to large numbers of people today. We now know approximately when the modern human and Neanderthal lineages separated. We now also know that when these lineages reencountered each other, they had evolved to such an extent that they were at the very limit of biological compatibility. This raises a question: Were the Neanderthals the only archaic humans who interbred with our ancestors? Or were there other major hybridizations in our past?

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古代DNA打开了潘多拉魔盒

Ancient DNA Opens the Floodgates

来自东方的惊喜

A Surprise from the East

2008年，俄罗斯考古学家在西伯利亚南部阿尔泰山脉的丹尼索瓦洞穴中挖掘出一块小指骨。该洞穴以18世纪一位名叫丹尼的俄罗斯隐士命名，他曾居住于此。这块骨头的生长板尚未愈合，表明它来自一名儿童。由于骨头太小，无法进行放射性碳定年法测定，而且它是在洞穴中混杂的土壤层中发现的，该土壤层中还包含距今不到3万年和超过5万年的文物，因此其年代无法确定。挖掘负责人阿纳托利·德列维扬科推测，这块骨头的主人可能是现代人，因此样本被标记为现代人。另一种可能性是，这块骨头的主人可能是尼安德特人，因为在洞穴附近也发现了尼安德特人的遗骸。德列维扬^科将部分骨头寄给了德国的斯万特·帕博。

In 2008, Russian archaeologists dug up a pinky bone at Denisova Cave in the Altai Mountains of southern Siberia, named after an eighteenth-century Russian hermit named Denis who had made his home there. The bone’s growth plates were not fused, showing that the bone came from a child. Its date was uncertain, as it was too small to be dated by radiocarbon analysis, and it was found in a mixed-up soil layer of the cave that contained artifacts dating to both less than thirty thousand and more than fifty thousand years ago. The leader of the excavation, Anatoly Derevianko, reasoned that the bone’s owner could have been a modern human, and the sample was so labeled. Alternatively, could the bone’s owner have been a Neanderthal, as Neanderthal remains were also found near the cave?¹ Derevianko sent part of the bone to Svante Pääbo in Germany.

由约翰内斯·克劳斯领导的帕博团队成功地从丹尼索瓦洞穴的骨骼中提取了线粒体DNA。2^其序列类型此前从未在超过一万个现代人类和七个尼安德特人的序列中观察到。现代人类的线粒体DNA与尼安德特人的线粒体DNA之间大约存在两百个突变差异。而从丹尼索瓦指骨中提取的新线粒体DNA与尼安德特人的线粒体DNA相比，存在近四百个差异。现代人类和尼安德特人的线粒体DNA序列均存在差异。根据突变积累速率，现代人类和尼安德特人的线粒体DNA序列估计在47万至36万年前就已分离。 ³丹尼索瓦指骨线粒体DNA中发现的突变差异数量表明，分离时间大约在80万至100万年前。这表明该指骨可能属于一个此前从未被取样过的古人类群体。 ⁴

Pääbo’s team, led by Johannes Krause, was successful in extracting mitochondrial DNA from the Denisova Cave bone.² Its sequence was of a type that had never before been observed in more than ten thousand modern human and seven Neanderthal sequences. There are around two hundred mutational differences separating the mitochondrial DNA of people living today from that of Neanderthals. The new mitochondrial DNA from the Denisova finger bone featured nearly four hundred differences from the mitochondrial DNA of both present-day humans and Neanderthals. Based on the rate at which mutations accumulate, mitochondrial DNA sequences from present-day humans and Neanderthals are estimated to have separated from each other 470,000 to 360,000 years ago.³ The number of mutational differences found in the mitochondrial DNA from the Denisova finger bone suggested a separation time of roughly eight hundred thousand to one million years ago. This suggested that the finger bone might belong to a member of a never-before-sampled group of archaic humans.⁴

然而，该人群的身份尚不明确。与尼安德特人不同，这里没有发现任何骨骼或工具制造风格方面的线索。对于尼安德特人而言，考古发现促成了基因组测序。而对于这个新发现的古老人群，基因数据则是先于基因组测序而来的。

The identity of the population, however, was unclear. No skeletons or toolmaking styles existed to give a hint, as they had in the case of the Neanderthals. For Neanderthals, archaeological discoveries had motivated the sequencing of a genome. For this new archaic group, the genetic data came first.

寻找化石的基因组

A Genome in Search of a Fossil

我第一次了解到这个此前不为人知的古人类群体是在2010年初，当时我正在德国莱比锡拜访斯万特·帕博的实验室。自从2007年加入帕博组建的尼安德特人基因组分析团队以来，我每年都会去莱比锡三次，这次是其中一次。一天晚上，帕博带我去啤酒花园，告诉我他们发现了新的线粒体序列。令人惊奇的是，丹尼索瓦人的指骨提供了迄今为止保存最完好的古代DNA样本之一。帕博筛选了数十个尼安德特人样本，发现其中只有少数样本含有高达4%的灵长类动物DNA，而这根指骨的灵长类动物DNA含量却高达70%左右。帕博和他的团队已经从这根小小的骨头中获得了比以往从尼安德特人身上获得的更多的全基因组数据（不仅仅是线粒体DNA）。他问我是否有兴趣帮忙分析数据。受邀分析丹尼索瓦人基因组是我科研生涯中最幸运的事。

I first found out about this previously unknown archaic human population in early 2010, while visiting Svante Pääbo’s laboratory in Leipzig, Germany. I was there on one of the thrice-yearly trips I had been making since joining the consortium that Pääbo put together in 2007 to analyze the Neanderthal genome. One evening, Pääbo took me out to a beer garden and told me about the new mitochondrial sequence they had come across. Miraculously, the Denisova finger bone had provided one of the best-preserved samples of ancient DNA ever found. While Pääbo had screened dozens of Neanderthal samples to find a few with up to 4 percent primate DNA, this finger bone had about 70 percent. Pääbo and his team had already been able to obtain more data on the whole genome (not just mitochondrial DNA) from this small bone than they had previously obtained from Neanderthals. He asked if I’d be interested in helping to analyze the data. The invitation to analyze the Denisovan genome was the greatest piece of good fortune I have had in my scientific career.

线粒体基因组表明，丹尼索瓦指骨来自人类群体中的某个个体。在现代人类和尼安德特人彼此分离之前，就已经有祖先与它们分道扬镳。但线粒体DNA仅记录了母系血统的信息，而母系血统只是构成每个人基因组的数万个谱系中的一小部分。要了解个体历史的真实情况，全面研究所有祖先谱系无疑更有价值。对于丹尼索瓦指骨而言，完整的基因组所呈现的图景与线粒体DNA所记录的截然不同。

The mitochondrial genome suggested that the Denisova finger bone came from an individual who was part of a human population that split from the ancestors of modern humans and Neanderthals before they separated from each other. But mitochondrial DNA only records information on the entirely female line, a tiny fraction of the many tens of thousands of lineages that have contributed to any person’s genome. To understand what really happened in an individual’s history, it is incomparably more valuable to examine all ancestral lineages together. For the Denisova finger bone, the whole genome painted a very different picture from what was recorded in the mitochondrial DNA.

全基因组分析的首要发现是，尼安德特人和丹尼索瓦洞穴新发现的人类彼此之间的亲缘关系比他们各自与现代人类的亲缘关系更近——这与线粒体DNA的分析结果有所不同。⁵^我们最终估计尼安德特人和丹尼索瓦人祖先群体的分离发生在47万至38万年前，而这两个古老群体与现代人类的共同祖先群体的分离发生在77万至55万年前。⁶^线粒体DNA的亲缘关系模式与基因组其他部分的共识并非必然矛盾，因为两个个体在任何DNA片段上拥有共同祖先的时间，至少与他们的祖先分化成不同群体的时间一样久远，有时甚至更久远。然而，通过研究全基因组，我们可以了解人群何时分化。我们认识到，全基因组包含了众多祖先的信息，因此我们可以寻找基因组中突变密度相对较低的短片段，这些片段反映了人群分化前不久的共同祖先。我们的研究结果表明，丹尼索瓦人是尼安德特人的近亲，但两者也存在很大差异，因为在许多尼安德特人特征出现在化石记录之前，丹尼索瓦人就已经与尼安德特人的祖先分化了。

The first revelation from the whole genome was that Neanderthals and the new humans from Denisova Cave were more closely related to each other than either was to modern humans—a different pattern from what was observed in mitochondrial DNA.⁵ We eventually estimated the separation between the Neanderthal and Denisovan ancestral populations to have occurred 470,000 to 380,000 years ago, and the separation between the common ancestral populations of both of these archaic groups and modern humans to have occurred 770,000 to 550,000 years ago.⁶ The different pattern of relatedness for mitochondrial DNA and the consensus of the rest of the genome were not necessarily a contradiction, as the time in the past when two individuals share a common ancestor at any section of their DNA is always at least as old as the time when their ancestors separated into populations, and can sometimes be far older. However, by studying the whole genome we can learn when the populations split, recognizing that the whole genome encompasses a whole multitude of ancestors so that we can search for short segments of the genome with a relatively low density of mutations reflecting a shared ancestor who lived just before the population separation. Our findings meant that the Denisovans were cousins of Neanderthals, but were also very different, having separated from Neanderthal ancestors before many Neanderthal traits appeared in the fossil record.

我们曾就如何称呼这个新发现的人群展开过激烈的辩论，最终决定使用一个通用的非拉丁语名称“丹尼索瓦人”，这个名字来源于他们最初被发现的洞穴，就像尼安德特人以德国的尼安德河谷命名一样。这个决定令一些同事感到不满，他们力主将其命名为一个新物种。名称——或许是阿尔泰人（Homo altaiensis），以丹尼索瓦洞穴所在的阿尔泰山脉命名。如今，俄罗斯新西伯利亚一家博物馆的展览就使用了“阿尔泰人”这一名称来描述丹尼索瓦的发现。然而，我们遗传学家一直不愿使用物种名称。长期以来，关于尼安德特人是否构成一个独立于现代人类的物种一直存在争议。一些专家将尼安德特人认定为人属（ Homo ）的一个独立物种（尼安德特人， Homo neanderthalensis），而另一些专家则将其视为现代人类的一个亚群（尼安德特人， Homo sapiens neanderthalensis）。将两个现存群体认定为不同物种通常是基于这样一个假设：这两个群体实际上不会杂交。^但我们现在知道，尼安德特人曾与现代人类成功杂交，而且事实上不止一次，这似乎削弱了他们是不同物种的论点。我们的数据显示，丹尼索瓦人是尼安德特人的近亲。因此，如果我们对尼安德特人是否属于一个物种尚存疑问，那么我们也需要对丹尼索瓦人是否属于一个物种持保留态度。传统上，判断已灭绝的人群是否具有足够的独特性以被认定为不同的物种，主要依据是骨骼的形状。而丹尼索瓦人的遗骸非常稀少，这更让我们有理由保持谨慎。

We had a heated debate about what to call the new population, and decided to use a generic non-Latin name, “Denisovans,” after the cave where they were first discovered, in the same way that Neanderthals are named after the Neander Valley in Germany. This decision distressed some of our colleagues, who lobbied for a new species name—perhaps Homo altaiensis, after the mountains where Denisova Cave is located. Homo altaiensis is now used in a museum exhibit in Novosibirsk in Russia that describes the discovery at Denisova. We geneticists, however, were reluctant to use a species name. There has long been contention as to whether Neanderthals constitute a species separate from modern humans, with some experts designating Neanderthals as a distinct species of the genus Homo (Homo neanderthalensis), and others as a subgroup of modern humans (Homo sapiens neanderthalensis). The designation of two living groups as distinct species is often based on the supposition that the two do not in practice interbreed.⁷ But we now know Neanderthals interbred successfully with modern humans and in fact did so on multiple occasions seems to undermine the argument that they are distinct species. Our data showed that Denisovans were cousins of Neanderthals, and thus if we are uncertain about whether Neanderthals are a species, we need to be uncertain about whether Denisovans are a species as well. Decisions about whether extinct populations are distinct enough to merit designation as different species are traditionally made based on the shapes of skeletons, and for Denisovans there are very few physical remains, providing even more reason to be cautious.

我们目前掌握的少量遗骸令人着迷。德雷维扬科和他的同事将几颗来自丹尼索瓦洞穴的臼齿寄给了帕博，这些臼齿含有与指骨密切相关的线粒体DNA。这些牙齿非常巨大，几乎超出了此前报道的所有人属牙齿的尺寸范围。人们认为，巨大的臼齿是对以大量坚硬的生食植物为主的饮食的一种生物适应。在丹尼索瓦人之前，已知拥有如此巨大牙齿且与我们亲缘关系最近的人类是主要以植物为食的南方古猿，例如著名的“露西”。“露西”的骨骼化石发现于埃塞俄比亚的阿瓦什河谷，距今已有三百多万年的历史。“露西”不使用工具，即使考虑到她较小的体型，她的大脑也只比黑猩猩略大一些，但她能够直立行走。因此，我们掌握的少量骨骼信息证实了丹尼索瓦人与尼安德特人和现代人类相比，具有非常显著的特征。

The few remains that we do have are intriguing. Derevianko and his colleagues sent Pääbo a couple of molar teeth from Denisova Cave that contained mitochondrial DNA closely related to the finger bone. These teeth were enormous, beyond the range of nearly all teeth previously reported in the genus Homo. Large molars are thought to be biological adaptations to a diet that includes lots of tough uncooked plants. Prior to the Denisovans, the humans closest to us who were known to have had teeth of this size were the primarily plant-eating australopithecenes, like the famous “Lucy,” whose skeleton, dating to more than three million years ago, was found in the Awash Valley of Ethiopia. “Lucy” did not use tools and had a brain only slightly larger than chimpanzees’ after correcting for her smaller body size, but she walked upright. Thus the little skeletal information we had confirmed the idea that Denisovans were very distinctive compared to both Neanderthals and modern humans.

杂交原理

The Hybridization Principle

我们利用全基因组序列，检验了丹尼索瓦人与某些现代人群的亲缘关系是否比其他人群更近。结果出乎意料。

Armed with a whole-genome sequence, we tested whether the Denisovans were more closely related to some present-day populations than others. This led to a huge surprise.

丹尼索瓦人在基因上与新几内亚人的亲缘关系比与欧亚大陆任何人群的亲缘关系都要近一些，这表明新几内亚人的祖先可能与丹尼索瓦人有过杂交。然而，丹尼索瓦洞穴到新几内亚的距离约为9000公里，而且新几内亚与亚洲大陆之间隔着一片海洋。新几内亚的气候也主要属于热带气候，与西伯利亚严酷的冬季截然不同，因此，适应一种环境的古人类不太可能在另一种环境中繁衍生息。

Denisovans were genetically a little closer to New Guineans than they were to any population from mainland Eurasia, suggesting that New Guinean ancestors had interbred with Denisovans. Yet the distance from Denisova Cave to New Guinea is around nine thousand kilometers, and New Guinea is, of course, separated by sea from the Asian mainland. The climate in New Guinea is also largely tropical, which could not be more different from Siberia’s bitter winters, and this makes it unlikely that archaic humans adapted to one environment would have flourished in the other.

我们对自己的研究结果持怀疑态度，并寻找其他解释。现代人类的祖先是否在数十万年前分裂成几个群体，其中一个群体与丹尼索瓦人关系更密切，并且对新几内亚人的祖先贡献大于对大多数其他现代人群祖先的贡献？然而，这种假设意味着，现代新几内亚人与丹尼索瓦人的遗传亲缘关系是由于数十万年前进入新几内亚人谱系的DNA片段造成的。在当今的新几内亚人基因组中，我们能够测量完整的古老祖先片段的长度，发现与丹尼索瓦人相关的片段比与尼安德特人相关的片段长约12%，这意味着与丹尼索瓦人相关的片段平均而言引入的时间要晚得多^。8

Skeptical of our findings, we cast around for alternative explanations. Had the ancestors of modern humans been divided into several populations hundreds of thousands of years ago, one of which was more closely related to Denisovans and contributed more to New Guineans’ ancestry than it contributed to the ancestry of most other present-day populations? However, this scenario would suggest that the genetic affinity to Denisovans in present-day New Guineans would be due to segments of DNA that entered the New Guinean lineage many hundreds of thousands of years ago. In New Guinean genomes today we were able to measure the size of intact archaic ancestry segments, and found that the ones related to Denisovans were about 12 percent longer than the ones related to Neanderthals, implying that the Denisovan-related segments had been introduced that much more recently on average.⁸

一旦古人类与现代人类混合，古人类贡献的DNA片段就会通过重组过程被切割，并以每条染色体每代一到两次拼接的频率与现代人类的DNA片段拼接在一起。正如第二章所述，尼安德特人祖先片段的长度对应于五万四千年至四万九千年前的混合时期。9^基于……由于丹尼索瓦人基因片段比新几内亚人基因片段更为常见，我们可以得出结论：丹尼索瓦人和新几内亚人祖先之间的杂交发生在五万九千年至四万四千年前。 ¹⁰

As soon as archaic populations mix with modern ones, the DNA segments contributed by archaic humans are chopped up by the process of recombination, spliced together with modern human segments at the rate of one or two splices per chromosome per generation. As discussed in chapter two, the length of Neanderthal ancestry segments corresponds to mixture between fifty-four and forty-nine thousand years ago.⁹ Based on how much longer the Denisovan segments were than the Neanderthal segments in New Guineans, we could conclude that the interbreeding between Denisovan and New Guinean ancestors occurred fifty-nine to forty-four thousand years ago.¹⁰

如今新几内亚人的基因组中有多少比例源自丹尼索瓦人？通过比较新几内亚人与其他非非洲人群相比，其古人类祖先基因证据的强度，我们估计新几内亚人约有3%至6%的祖先源自丹尼索瓦人。这还不包括约2%的尼安德特人祖先。因此，新几内亚人总祖先中约有5%至8%源自古人类。这是已知古人类对现代人类群体贡献最大的一次。

What percentage of New Guinean genomes today derives from Denisovans? By measuring how much stronger the genetic evidence of archaic ancestry is in New Guineans compared to other non-Africans, we estimated that about 3 to 6 percent of New Guinean ancestry derives from Denisovans. That is above and beyond the approximately 2 percent from Neanderthals. Thus in total, 5 to 8 percent of New Guinean ancestry comes from archaic humans. This is the largest known contribution of archaic humans to any present-day human population.

丹尼索瓦人的发现证明，在现代人类从非洲和近东迁徙的过程中，古人类与现代人类之间的杂交并非偶然事件。迄今为止，已对两个古人类群体——尼安德特人和丹尼索瓦人——的DNA进行了测序，在这两个案例中，数据都揭示了此前未知的现代人类与古人类之间的杂交现象。如果下一个新发现的古人类群体的DNA测序结果也指向此前未知的杂交事件，我不会感到惊讶。

The Denisova discovery proved that interbreeding between archaic and modern humans during the migration of modern humans from Africa and the Near East was not a freak event. So far, DNA from two archaic human populations—Neanderthals and Denisovans—has been sequenced, and in both cases, the data made it possible to detect hybridization between modern and archaic humans that had been previously unknown. I would not be surprised if DNA sequenced from the next newly discovered archaic population will also point to a previously unknown hybridization event.

突破赫胥黎防线

Breaching Huxley’s Line

鉴于西伯利亚和新几内亚之间遥远的距离，丹尼索瓦人和新几内亚人的祖先究竟在哪里发生了杂交？

Where, given the vast distance between Siberia and New Guinea, did interbreeding between Denisovans and the ancestors of New Guineans occur?

我们最初的猜测是亚洲大陆，或许是印度或中亚，位于一条从非洲到新几内亚的合理的人类迁徙路线上。如果真是如此，那么东亚大陆或南亚大陆缺乏丹尼索瓦人相关血统的原因就可以解释为，后来现代人类（不具备丹尼索瓦人血统）进行了多次扩张，取代了原本拥有丹尼索瓦人血统的人群。这些后期的迁徙对现代新几内亚人的DNA贡献不大，这或许可以解释为什么如今新几内亚人群中丹尼索瓦人血统的比例相对较高。

Our first guess was mainland Asia, perhaps India or central Asia, on a plausible human migratory path from Africa to New Guinea. If this had been the case, the lack of much Denisovan-related ancestry in mainland East or South Asia could be explained by later waves of expansion on the part of modern humans without Denisovan-related ancestry, who replaced populations having Denisovan-related ancestry. That these later migrations did not contribute much to the DNA of present-day New Guineans might account for the relatively high proportion of Denisovan-related ancestry in New Guinean populations today.

对现代人群中丹尼索瓦人相关血统地理分布的初步观察似乎支持了这一观点。我们采集了来自西南太平洋岛屿、东亚、南亚和澳大利亚的现代人类的DNA，并估算了他们各自所含的丹尼索瓦人相关血统比例。我们发现，东南亚岛屿，尤其是菲律宾以及新几内亚和澳大利亚等面积较大的岛屿上的土著居民，其丹尼索瓦人血统比例最高（我这里所说的“土著居民”指的是在农业传播相关的人口迁徙之前就已定居于此的人群）。 ¹¹这些人群主要分布在赫胥黎线以东，赫胥黎线是一条天然分界线，将新几内亚、澳大利亚和菲律宾与印度尼西亚西部和亚洲大陆分隔开来。这条线由十九世纪英国博物学家阿尔弗雷德·罗素·华莱士描述，并由他的同时代生物学家托马斯·亨利·赫胥黎加以改编，以突出生活在两侧动物的差异。例如，它大致构成了西侧有胎盘哺乳动物和东侧有袋类动物之间的分界线。它与深海海沟相对应，这些海沟即使在冰河时期也形成了阻碍动植物迁徙的地理屏障。海平面曾比现在低一百米之多。令人惊叹的是，五万年前的现代人类竟然能够跨越这道屏障。这些先驱者的确成功跨越了这道屏障，但这必定十分艰难。生活在赫胥黎线以东、拥有丹尼索瓦人血统的现代人类——我们发现，他们是如今丹尼索瓦人血统比例最高的人群，也是新几内亚人、澳大利亚人和菲律宾人的祖先——很可能也像与他们共享这片土地的动物一样，受到这道屏障的保护，免受来自亚洲的进一步迁徙。

A first glance at the geographic distribution of Denisovan-related ancestry in present-day people seemed to support this idea. We collected DNA from present-day humans from the islands of the Southwest Pacific and from East Asia, South Asia, and Australia, and estimated how much Denisovan-related ancestry each of them had. We found the largest amounts of ancestry in indigenous populations in the islands off Southeast Asia and especially in the Philippines and the very large islands of New Guinea and Australia (by the word “indigenous” I refer to people who were established prior to the population movements associated with the spread of farming).¹¹ The populations in question are largely east of Huxley’s Line, a natural boundary that separates New Guinea, Australia, and the Philippines from the western parts of Indonesia and the Asian mainland. This line was described by the nineteenth-century British naturalist Alfred Russel Wallace, and adapted by his contemporary the biologist Thomas Henry Huxley to highlight differences in the animals living on either side, for example, it roughly forms the boundary between placental mammals to the west and marsupials to the east. It corresponds to deep ocean trenches that have formed geographical barriers to the crossing of animals and plants, even in ice ages when sea levels were up to one hundred meters lower. It is remarkable that modern humans after fifty thousand years ago made it across this barrier. These pioneers did manage to cross, but it must have been difficult. Modern humans with Denisovan-related ancestry living east of Huxley’s Line—the ancestors of New Guineans, Australians, and Philippine populations who we found are the groups with the largest proportions of Denisovan ancestry today—are likely to have been protected by the same barrier from further migrations from Asia, just like the animals with whom they share their landscape.

但深入分析表明，亚洲腹地的人口混合现象并非表面看起来那么容易解释。虽然赫胥黎线以东的一些人群拥有大量的丹尼索瓦人血统，但情况与赫胥黎线以西截然不同。最显著的例子是，印度和苏门答腊沿岸安达曼群岛的土著狩猎采集者，以及东南亚大陆马来半岛的土著狩猎采集者，他们的祖先谱系与新几内亚人和澳大利亚土著居民的谱系差异同样显著，但他们却几乎没有丹尼索瓦人血统。此外，在北京附近天元洞发现的距今约四万年的人类遗骸的全基因组测序数据中，也没有发现丹尼索瓦人血统比例升高的证据。该遗骸的基因组测序工作由帕博及其实验室在几年后完成。¹²如果这种杂交发生在亚洲大陆，并且携带丹尼索瓦人相关血统的现代人类随后扩散到各地，那么该地区的多个人群以及东亚的古代人类都应该携带与新几内亚人相当数量的丹尼索瓦人相关血统。但这并非我们所观察到的。

But a deeper look suggests that population mixture in the heart of Asia is not as easy an explanation as it might at first seem. Although some populations east of Huxley’s Line have large amounts of Denisovan-related ancestry, the situation is very different to the west. Most notably, the indigenous hunter-gatherers of the Andaman Island chain off the coasts of India and Sumatra, and also the indigenous hunter-gatherers of the Malay Peninsula of mainland Southeast Asia, descend from lineages just as divergent as those in indigenous New Guineans and Australians, and yet they do not have much Denisovan-related ancestry. There is also no evidence of elevated Denisovan-related ancestry in genome-wide data from the approximately forty-thousand-year-old human of Tianyuan Cave near Beijing in China, which was sequenced several years later by Pääbo and his laboratory.¹² Had the interbreeding occurred in mainland Asia, and modern humans carrying Denisovan-related ancestry then spread all over, multiple populations of the region as well as ancient humans from East Asia would be expected to carry Denisovan-related ancestry in amounts comparable to what is seen in New Guineans. But this is not what we observe.

对于亚洲东南端岛屿、新几内亚和澳大利亚上大量丹尼索瓦人血统的最简单解释是，这些岛屿附近——无论是在岛屿本身还是在东南亚大陆——都发生了通婚，但无论哪种情况，都发生在远离丹尼索瓦洞穴的热带地区。然而，人类学家海部洋介在我2011年参加的一次讲座中指出，岛屿附近通婚的假设很难与该地区缺乏能够合理反映高脑容量人群存在的考古文物相吻合。丹尼索瓦人是尼安德特人和现代人的近亲。凯夫还指出，迄今为止，该地区尚未发现同时期的大头骨骨骼。这让我认为，更可能的是，杂交发生在中国南方或东南亚大陆。在中国中北部陕西省大理、东北辽宁省金牛山以及东南部广东省马坝，都发现了距今约20万年的古人类遗骸，这些遗骸的骨骼特征与丹尼索瓦人更为吻合。印度中部纳尔默达河畔发现的古人类遗骸，其年代可能距今约7.5万年。中印两国政府的规定使得骨骼材料的出口较为复杂，但世界一流的古DNA实验室已在中国建立，印度也正在建设中。这些样本的DNA分析有望带来非凡的发现。

The simplest explanation for the large fractions of Denisovan-related ancestry on the islands off the southeastern tip of Asia and in New Guinea and Australia would be the occurrence of interbreeding near the islands—on the islands themselves or in mainland Southeast Asia—but in either case in a tropical region very far from Denisova Cave. However, the anthropologist Yousuke Kaifu pointed out in a talk I attended in 2011 that the hypothesis of interbreeding near the islands is difficult to square with an absence of archaeological artifacts in the region that could plausibly reflect the presence of a big-brained cousin of Neanderthals and modern humans. Kaifu also pointed out that no big-skulled skeletons from this time in this region have so far been found. This makes me think that it is more likely that interbreeding occurred in southern China or mainland Southeast Asia. There are archaic human remains from Dali in Shaanxi province in north-central China, from Jinniushan in Liaoning in northeastern China, and from Maba in Guangdong in southeastern China, all dating to around two hundred thousand years ago, all of which are more plausible skeletal matches for the Denisovans. An archaic human from Narmada in central India may date to around seventy-five thousand years ago. Chinese and Indian government rules complicate the export of skeletal material, but world-class ancient DNA labs have now been established in China and are beginning to be built in India. DNA from these samples could lead to extraordinary insights.

认识一下澳大利亚丹尼索瓦人

Meet the Australo-Denisovans

虽然与我们采集样本并进行测序的尼安德特人是近亲，但与新几内亚人祖先杂交的古人类与西伯利亚丹尼索瓦人并非近亲。当我们分析现代新几内亚人和澳大利亚人的基因组，并计算他们与西伯利亚丹尼索瓦人之间的DNA碱基差异数量，以估算他们的祖先何时从共同的祖先群体中分离出来时，我们发现，在基因组的各个区域，差异数量至少与40万至28万年前发生的群体分裂的预期值相当。 ¹³这意味着，西伯利亚丹尼索瓦人的祖先与为新几内亚人提供祖先的丹尼索瓦人谱系分离的时间，大约比丹尼索瓦人祖先与尼安德特人分离的时间早三分之二。

While the interbreeding Neanderthals were close relatives of those we obtained samples from and sequenced, the archaic people who interbred with the ancestors of New Guineans were not close relatives of the Siberian Denisovans. When we examined the genomes of present-day New Guineans and Australians, and counted the number of DNA letter differences between them and the Siberian Denisovans to estimate when their ancestors separated from a common parent population, we discovered that everywhere in the genome, the number of differences was at least what would be expected for a population split that occurred 400,000 to 280,000 years ago.¹³ This meant that the ancestors of the Siberian Denisovans separated from the Denisovan lineage that contributed ancestry to New Guineans two-thirds of the way back to the separation of the ancestors of Denisovans from Neanderthals.

鉴于两族之间的遥远关系，它们可能拥有不同的适应方式，这可以解释它们如何在如此不同的气候条件下繁衍生息。考虑到丹尼索瓦人种群的非凡多样性——其族群成员之间的时间间隔更长——比起现今人群，丹尼索瓦人内部的分化更为复杂——因此，将他们视为一个广泛的人类类别是合理的，其中一支演化成了与新几内亚人杂交的古老人群的祖先，另一支则演化成了西伯利亚丹尼索瓦人。很可能还存在我们尚未采集到样本的其他丹尼索瓦人群体。或许我们甚至应该将尼安德特人也纳入这个广泛的丹尼索瓦人家族之中。

In light of the remote relationship, the two groups probably had different adaptations, which would explain how they were able to thrive in such different climates. Given the extraordinary diversity of Denisovans—with much more time separation among their populations than exists among present-day groups—it makes sense to think of them as a broad category of humans, one branch of which became the ancestors of the archaic population that interbred with New Guineans and another that became Siberian Denisovans. Most likely there are other Denisovan populations as well that we haven’t sampled at all. Maybe we should even consider Neanderthals as part of this broad Denisovan family.

我们从未给与迁徙到东南亚岛屿的现代人类杂交的丹尼索瓦人相关人群赋予一个专门的名称，但我倾向于称他们为“澳大利亚-丹尼索瓦人”，以强调他们可能分布在南部地区。人类学家克里斯·斯特林格（Chris Stringer）则更倾向于称他们为“巽他丹尼索瓦人”，这个名称源于连接印度尼西亚大部分岛屿和东南亚大陆的巽他陆地。 ¹⁴但如果杂交发生在如今的东南亚大陆、中国或印度，那么这个名称就不准确了。

We never assigned a special name to the Denisovan-related population that interbred with modern humans who migrated to the islands off Southeast Asia, but I like to call them “Australo-Denisovans” to highlight their likely southern geographical distribution. Anthropologist Chris Stringer prefers “Sunda Denisovans” after the landmass that joined most of the Indonesian islands to the Southeast Asian mainland.¹⁴ But this would not be an accurate name if the interbreeding occurred in what is now mainland Southeast Asia, China, or India.

人们很容易认为，澳大利亚-丹尼索瓦人、丹尼索瓦人和尼安德特人起源于最早走出非洲的直立人种群，而现代人类则起源于留在非洲的直立人 种群，但这种想法是错误的。在非洲以外发现的最古老的直立 人骨骼化石分别位于格鲁吉亚的德马尼西遗址（距今约180万年）和印度尼西亚的爪哇岛（年代几乎相同）。如果最早走出非洲的直立人是丹尼索瓦人和尼安德特人的祖先，那么这些种群与现代人类的分化时间至少与现代人类向欧亚大陆扩散的时间一样久远——这远远超出了基因观测结果的合理范围。基因数据显示，分化时间在77万至55万年前，这比180万年前的种群分离时间要近得多。

It is tempting to think that the Australo-Denisovans, Denisovans, and Neanderthals descend from the first Homo erectus populations that expanded out of Africa, and that modern humans descend from the Homo erectus populations that stayed in Africa, but that would be wrong. The oldest Homo erectus skeletons outside of Africa have been found at the site of Dmanisi in Georgia dating to around 1.8 million years ago, and on the island of Java in Indonesia dating to almost the same time. If Homo erectus from the first radiation out of Africa was ancestral to the Denisovans and Neanderthals, then the split of these populations from modern humans would be at least as old as the dispersal to Eurasia—far too old to be consistent with the genetic observations. The genetic data give a split date of 770,000 to 550,000 years ago, too recent to be consistent with a 1.8-million-year-old population separation.

然而，化石记录中确实存在一个符合时代背景的祖先候选者，其年代远晚于直立人走出非洲，但晚于智人。1907年在德国海德堡附近发现的一具大头骨骨骼，经测定距今约60万年，^很可能属于现代人类和尼安德特人的祖先物种，并由此推断，也可能属于丹尼索瓦人的祖先。海德堡人（Homo heidelbergensis）通常被认为是现代人类和尼安德特人的^祖先。海德堡人被认为是西欧亚大陆和非洲的物种，但并非东欧亚大陆的物种。然而，来自澳大利亚-丹尼索瓦人的遗传证据表明，海德堡人的谱系可能也早已在东欧亚大陆建立。丹尼索瓦人发现的深远意义之一在于，东欧亚大陆是人类进化的核心阶段，而非西方人通常认为的次要阶段。

There is, however, a candidate in the fossil record for an ancestor in the right period, dating to long after the Homo erectus out-of-Africa migration but after the Homo sapiens one. A big-skulled skeleton found near Heidelberg in Germany in 1907 and dated to around six hundred thousand years ago¹⁵ was plausibly from a species that was ancestral to modern humans and Neanderthals,¹⁶ and by implication, Denisovans too. Homo heidelbergensis is often viewed as both a West Eurasian and an African species, but not an East Eurasian species. However, the genetic evidence from the Australo-Denisovans shows that the Homo heidelbergensis lineage may have been established very anciently in East Eurasia too. One of the profound implications of the Denisovan discovery was that East Eurasia is a central stage of human evolution and not a sideshow as westerners often assume.

因此，我们现在可以获得来自四个高度分化的人类群体的全基因组数据，这些群体可能都拥有较大的大脑，并且都生活在距今七万年以内。这些群体包括现代人类、尼安德特人、西伯利亚丹尼索瓦人和澳大利亚丹尼索瓦人。此外，我们还需要加上生活在如今印度尼西亚弗洛勒斯岛的矮小人类——这些“霍比特人”很可能起源于早期直立人，而直立人的后代在七十万年前就已抵达弗洛勒斯岛，并因深海而与世隔绝。 ¹⁷这五个人类群体，以及可能更多尚未发现的、生活在当时的群体，彼此之间相隔数十万年的进化历程。这比当今亲缘关系最远的人类谱系之间的分离时间还要长——例如，非洲南部桑人狩猎采集者与其他所有人之间的分离时间。七万年前，世界上居住着各种各样的人类，我们拥有越来越多人类的基因组，这使我们能够回溯到人类比今天更加多样化的时代。

So we now have access to genome-wide data from four highly divergent human populations that all likely had big brains, and that were all still living more recently than seventy thousand years ago. These populations are modern humans, Neanderthals, Siberian Denisovans, and Australo-Denisovans. To these we need to add the tiny humans of Flores island in present-day Indonesia—the “hobbits” who likely descend from early Homo erectus whose descendants arrived at Flores island before seven hundred thousand years ago and became isolated there by deep waters.¹⁷ These five groups of humans and probably more groups still undiscovered who lived at that time were each separated by hundreds of thousands of years of evolution. This is greater than the separation times of the most distantly related human lineages today—for example, the one highly represented in San hunter-gatherers from southern Africa and everyone else. Seventy thousand years ago, the world was populated by very diverse human forms, and we have genomes from an increasing number of them, allowing us to peer back to a time when humanity was much more variable than it is today.

远古接触如何帮助了现代人类

How Archaic Encounters Helped Modern Humans

现代人类与丹尼索瓦人杂交的生物学遗产是什么？在当今任何人群中，丹尼索瓦人相关血统比例最高的是新几内亚人和澳大利亚人，以及他们的后裔。 ¹⁸ 然而，当我们获得更完善的数据并采用更灵敏的技术后，我们发现即使在亚洲大陆也存在一些丹尼索瓦人相关血统，尽管比例要低得多。 ¹⁹而正是来自亚洲大陆，我们才得以了解其生物学影响。

What is the biological legacy of the interbreeding between modern humans and Denisovans? The highest proportion of Denisovan-related ancestry in any present-day population is found in New Guineans and Australians and the people to whom they contributed ancestry.¹⁸ However, once we obtained better data and used more sensitive techniques, we found that there is also some Denisovan-related ancestry, albeit far less, even in mainland Asia,¹⁹ and it is from the mainland that we have a clue about its biological effects.

东亚人中与丹尼索瓦人相关的血统比例约为新几内亚人的25%，约占东亚人基因组的0.2%，在南亚部分地区则高达0.3%至0.6%。 ²⁰我们目前尚无法确定亚洲大陆和东南亚岛屿上的丹尼索瓦人相关血统是否源自同一古老人群，还是源自不同的人群。如果这些血统源自截然不同的来源，那么我们将发现又一个古老人类与现代人类杂交的例子。但无论其起源如何，丹尼索瓦人的杂交都具有重要的生物学意义。

The Denisovan-related ancestry in East Asians is about a twenty-fifth of that seen in New Guineans—it comprises about 0.2 percent of East Asians’ genomes, rising to up to 0.3–0.6 percent in parts of South Asia.²⁰ We have not yet been able to determine if the Denisovan-related ancestry in mainland Asia and the islands off Southeast Asia comes from the same archaic population or from different ones. If the ancestry comes from very different sources, we would be detecting yet another instance of archaic human interbreeding with modern humans. But whatever its origin, the Denisovan interbreeding was biologically significant.

近几年最引人注目的基因组学发现之一，是红细胞中一个活跃基因的突变，这种突变使生活在西藏高海拔地区的人们能够在缺氧环境中生存。拉斯穆斯·尼尔森及其同事的研究表明，发生这种突变的DNA片段与西伯利亚丹尼索瓦人的基因组匹配度远高于与尼安德特人或现代非洲人的DNA匹配度。 ²¹这表明，亚洲大陆的一些丹尼索瓦人亲属可能已经具备了适应高海拔环境的能力，而藏族的祖先通过与丹尼索瓦人的杂交继承了这种能力。考古证据表明，西藏高原的第一批居民在大约11000年前开始季节性地居住在那里，而以农业为基础的永久性定居则始于大约3600年前。 ²²这种突变的频率很可能是在此之后才迅速增加的，这一推测可以通过对古代藏族人的DNA研究直接验证。

One of the most striking genomic discoveries of the past few years is a mutation in a gene that is active in red blood cells and that allows people who live in high-altitude Tibet to thrive in their oxygen-poor environment. Rasmus Nielsen and colleagues have shown that the segment of DNA on which this mutation occurs matches much more closely to the Siberian Denisovan genome than to DNA from Neanderthals or present-day Africans.²¹ This suggests that some Denisovan relatives in mainland Asia may have harbored an adaptation to high altitude, which the ancestors of Tibetans inherited through Denisovan interbreeding. Archaeological evidence shows that the first inhabitants of the Tibetan high plateau began living there seasonally after eleven thousand years ago, and that permanent occupation based on agriculture began around thirty-six hundred years ago.²² It is likely that the mutation increased rapidly in frequency only after these dates, a prediction that will be possible to test directly through DNA studies of ancient Tibetans.

与尼安德特人的杂交帮助现代人类适应了新的环境，正如与丹尼索瓦人的杂交一样。我们和其他研究人员发现，在与角蛋白生物学相关的基因中，现代欧洲人和东亚人平均继承的尼安德特人血统远高于大多数其他基因组。 ²³这表明，尼安德特人携带的角蛋白生物学基因版本在自然选择的压力下得以在非非洲人群中保留下来，这或许是因为角蛋白是皮肤和毛发的重要组成部分，而皮肤和毛发对于抵御寒冷环境（例如现代人类正在迁徙的环境，以及尼安德特人已经适应的环境）至关重要。

Interbreeding with Neanderthals helped modern humans to adapt to new environments just as interbreeding with Denisovans did. We and others showed that at genes associated with the biology of keratin proteins, present-day Europeans and East Asians have inherited much more Neanderthal ancestry on average than is the case for most other groups of genes.²³ This suggests that versions of keratin biology genes carried by Neanderthals were preserved in non-Africans by the pressures of natural selection, perhaps because keratin is an essential ingredient of skin and hair, which are important for providing protection from the elements in cold environments such as the ones that modern humans were moving into and to which Neanderthals were already adapted.

超古人类

Superarchaic Humans

鉴于丹尼索瓦人和尼安德特人在基因上比他们各自与现代人类的亲缘关系更近，人们理所当然地会认为，他们与未接受过这两种古老人群基因输入的现代人群（即撒哈拉以南非洲人）的亲缘关系应该大致相同。然而，我们发现撒哈拉以南非洲人与尼安德特人的亲缘关系比与丹尼索瓦人的亲缘关系略近。 ²⁴这必然反映了我们之前未知的另一种杂交现象。我们观察到的这种模式只能用丹尼索瓦人与一个高度分化、至今仍未知的古老人群杂交来解释——这个古老人群的DNA与非洲人和尼安德特人几乎没有关联，并且早在现代人类、尼安德特人和丹尼索瓦人的共同祖先彼此分离之前就已经分离了。

Given that Denisovans and Neanderthals are genetically closer to each other than either is to modern humans, it would be reasonable to expect them to be equidistantly related to present-day populations that have not received genetic input from either of these archaic populations—that is, to sub-Saharan Africans. Yet we found sub-Saharan Africans to be slightly more closely related to Neanderthals than to Denisovans.²⁴ This must reflect another example of interbreeding we didn’t know about. The pattern we observed could only be explained by Denisovan interbreeding with a deeply divergent, still unknown archaic population—one from which Africans and Neanderthals have little or no DNA, and which separated from the common ancestors of modern humans, Neanderthals, and Denisovans well before their separation from each other.

丹尼索瓦人基因组中存在未知远古基因贡献的证据是，在所有非洲人共有的基因组位点上，这种突变在尼安德特人中的出现频率高于丹尼索瓦人。由于这些突变是所有非洲人都携带的，我们知道它们发生在很久以前，因为在人类中，一种不受自然选择影响的新突变通常需要大约一百万年或更长时间才能在人群中传播并达到100%的频率。唯一能解释丹尼索瓦人没有携带这些突变的方法是，丹尼索瓦人的祖先曾与一个与丹尼索瓦人、尼安德特人和现代人类分化时间非常久远的群体杂交，以至于几乎所有现代人类都携带了这种新的突变。

The evidence for an unknown archaic contribution to Denisovans is that at locations in the genome where all Africans share a mutation, the mutation is more often seen in Neanderthals than in Denisovans. Because these are mutations that all Africans carry, we know that they occurred long ago, as it typically takes around a million years or more in humans for a new mutation not under natural selection to spread throughout a population and achieve 100 percent frequency. The only way to explain the fact that Denisovans do not also share these mutations is if the ancestors of the Denisovans interbred with a population that diverged from Denisovans, Neanderthals, and modern humans so long ago that nearly all modern humans carry the new mutation.

通过研究在现代非洲人中发生频率为100%的突变，并测量这些突变与尼安德特人基因组匹配的概率高于与丹尼索瓦人基因组匹配的概率，我们估计，与丹尼索瓦人杂交的未知古人类群体在大约140万至90万年前首次从现代人类的谱系中分离出来，并且该未知古人类群体至少贡献了3%至6%的丹尼索瓦人相关祖先成分。由于我们对人类突变率的了解有限，这个时间点尚不明确。然而，即使突变率存在不确定性，我们仍然可以估计……通过对相对年代的合理推断，我们可以确信，这个此前未被取样的人类群体与丹尼索瓦人、尼安德特人和现代人类的分化时间大约是后者的两倍。我将这个群体称为“超古人类”，因为他们代表着比丹尼索瓦人更深远的分化谱系。他们是我所说的“幽灵”群体，我们没有这个群体的纯种基因数据，但可以通过他们对后世人类的基因贡献来推断他们曾经存在过。

By examining mutations that occur at 100 percent frequency in present-day Africans, and measuring the excess rate at which they matched the Neanderthal over the Denisovan genome, we estimated that the unknown archaic population that interbred into Denisovans first split off from the lineage leading to modern humans 1.4 to 0.9 million years ago and that this unknown archaic population contributed at least 3 to 6 percent of Denisovan-related ancestry. The date is shaky, as knowledge of the human mutation rate is poor. However, even with the uncertainty about the mutation rate, we can estimate relative dates reasonably well, and we can be confident that this previously unsampled human population split off at about twice the separation time of Denisovans, Neanderthals, and modern humans. I think of this group as “superarchaic” humans, as they represent a more deeply splitting lineage than Denisovans. They are what I call a “ghost” population, a population we do not have data from in unmixed form, but whose past existence can be detected from its genetic contributions to later people.

欧亚大陆是人类进化的温室

Eurasia as a Hothouse of Human Evolution

结合考古学和遗传学数据，我们可以确信，在过去两百万年中，现代人类和古代人类谱系之间至少发生了四次重大的人口分离。

From a combination of archaeological and genetic data, we can be confident of at least four major population separations involving modern and archaic human lineages over the last two million years.

骨骼证据表明，人类首次大规模迁徙至欧亚大陆至少发生在180万年前，当时直立人从非洲迁徙而来。基因证据表明，大约在140万至90万年前，第二个谱系从现代人类的祖先谱系中分离出来，形成了我们通过其与丹尼索瓦人祖先的基因混合而发现的超古老群体。该群体很可能贡献了高度分化的丹尼索瓦人线粒体DNA序列，而该序列与尼安德特人和现代人类在同一时期拥有共同的祖先。基因学还表明，在77万至55万年前发生了第三次重大分化，当时现代人类的祖先与丹尼索瓦人和尼安德特人分离；随后，丹尼索瓦人和尼安德特人在47万至38万年前彼此分离。

The skeletal evidence shows that the first important spread of humans to Eurasia occurred at least 1.8 million years ago, bringing Homo erectus from Africa. The genetic evidence suggests that a second lineage split from the one leading to modern humans around 1.4 to 0.9 million years ago, giving rise to the superarchaic group that we have evidence of through its mixture with the ancestors of Denisovans and that plausibly contributed the highly divergent Denisovan mitochondrial DNA sequence that shares a common ancestor with both Neanderthals and modern humans in this time frame. Genetics also suggests a third major split 770,000 to 550,000 years ago when the ancestors of modern humans separated from Denisovans and Neanderthals, followed by Denisovans and Neanderthals from each other 470,000 to 380,000 years ago.

这些基因年代测定依赖于突变率的估算，并且会随着这些估算的日益精确而改变。人们很容易陷入试图在基因年代和考古记录之间建立清晰关联这一陷阱，但一旦出现新的基因突变发生率估算，年代就会发生变化，导致整个理论体系崩塌。然而，这些分裂的顺序以及不同人群之间的差异可以通过遗传学方法很好地确定。

These genetic dates depend on estimates of the mutation rate and will change as those estimates become more exact. It is easy to get ensnared in trying to establish neat correlations between genetic dates and the archaeological record, only to have dates shift when a new genetic estimate of the rate of occurrence of new mutations comes along, causing the whole intellectual edifice to come tumbling down. However, the order of these splits and the distinctness of the populations can be determined well from genetics.

通常的假设是，这四个分裂都对应于非洲的祖先人群向欧亚大陆扩张。但事实真的非得如此吗？

The usual assumption is that all four of these splits correspond to ancestral populations in Africa expanding into Eurasia. But does this really have to be the case?

现代人类起源于非洲的论点源于这样的观察：现代人类中分化最深的谱系在非洲狩猎采集者（例如南部非洲的桑人和中部非洲的俾格米人）中最为显著。具有现代人类解剖特征的最古老人类遗骸也发现于非洲，其年代可追溯至约30万年前。然而，指向非洲起源的现代人群基因比较只能探究过去几十万年间形成的人群结构，而这段时期正是现代人群祖先分化的时间范围。掌握了古代DNA数据后，我们发现，在我们掌握DNA数据的四个最古老的人类谱系中，分化最深的三个谱系仅在欧亚大陆出土的人类标本中有所体现：尼安德特人、丹尼索瓦人以及在西伯利亚丹尼索瓦人中留下痕迹的“超古老”人群。

The argument that modern humans radiated from Africa comes from the observation that the most deeply divergent branches among present-day humans are most strongly represented in African hunter-gatherers (such as San from southern Africa and central African Pygmies). The oldest remains of humans with anatomically modern features are also found in Africa and date to up to around three hundred thousand years ago. However, the genetic comparisons of present-day populations that point to an origin in Africa can only probe the population structure that has arisen in the last couple of hundred thousand years, the time frame of the diversification of the ancestors of present-day populations. With ancient DNA data in hand, we are confronted with the observation that of the four deepest human lineages from which we have DNA data, the three most deeply branching ones are represented only in human specimens excavated from Eurasia: the Neanderthals, the Denisovans, and the “superarchaic” population that left traces among the Siberian Denisovans.

我们在欧亚大陆检测到最古老的分化谱系，部分原因可能是科学家所说的“确定性偏差”：几乎所有古代DNA研究都是在欧亚大陆而非非洲进行的，因此，新的谱系自然也发现于欧亚大陆。或许，如果我们拥有与欧亚大陆一样多的来自非洲的古老DNA序列，我们就能在那里发现比超古老谱系更早与现代人类和尼安德特人分化的谱系。

Part of the reason we detect the oldest splitting lineages in Eurasians may be what scientists call “ascertainment bias”: the fact that almost all ancient DNA work has been done in Eurasia rather than in Africa, and so naturally that is where new lineages have been discovered. Perhaps if we had as many archaic ancient DNA sequences from Africa as we do from Eurasia, we would find lineages there that split from modern humans and Neanderthals even more deeply in time than the superarchaic.

但另一种可能性也浮现出来，那就是现代人类、尼安德特人和丹尼索瓦人的祖先实际上生活在欧亚大陆，他们是最初从非洲迁徙出来的直立人的后裔。在这种情况下，后来发生了从欧亚大陆返回非洲的迁徙，为后来演化成现代人类的人群提供了最初的奠基者。这一理论的吸引力在于其简洁性：它只需要一次非洲和欧亚大陆之间的大规模人口迁徙就能解释现有数据。超古人类群体和现代人类、丹尼索瓦人和尼安德特人的祖先群体都可能起源于欧亚大陆，而无需另外两次走出非洲的迁徙。因为后来只有一次迁徙回到非洲，与那里的现代人类建立了共同的祖先关系。

But another possibility suggests itself, which is that the ancestral population of modern humans, Neanderthals, and Denisovans actually lived in Eurasia, descending from the original Homo erectus spread out of Africa. In this scenario, there was later migration back from Eurasia to Africa, providing the primary founders of the population that later evolved into modern humans. The attraction of this theory is its economy: it requires one less major population movement between Africa and Eurasia to explain the data. The superarchaic population and the ancestral population of modern humans, Denisovans, and Neanderthals could both have arisen within Eurasia, without requiring two further out-of-Africa migrations, as long as there was just one later migration back into Africa to establish shared ancestry with modern humans there.

从经济角度出发的论证并不能作为证据。但更重要的是，众多谱系和基因混合的证据应该会动摇我们对一个被许多人奉为圭臬的假设的信心，即非洲一直是人类进化所有重大事件的中心。根据骨骼记录，可以肯定的是，在两百万年前，非洲在我们人类谱系的进化中扮演了核心角色，正如我们在发现生活在非洲的直立行走猿类（比智人早数百万年）时所知的那样。我们也知道，非洲在解剖学意义上的现代人类的起源中也扮演了核心角色，这基于在非洲发现的、具有解剖学意义上的现代人类特征的骨骼（时间大约在三十万年前），以及过去五万年间人类从非洲和近东扩散的遗传证据。但是，两百万年前到大约三十万年前这段时期又如何呢？在这一时期的大部分时间里，我们发现的非洲人类骨骼与现代人类的亲缘关系，并不比欧亚大陆的人类骨骼更近。 ²⁵近二十年来，一种观点逐渐转变，认为既然我们的祖先在两百万年前和三十万年前都曾出现在非洲，那么我们的祖先一定一直生活在那里。但欧亚大陆是一个丰富多样的超级大陆，现代人类的祖先完全有可能在返回非洲之前，在那里停留过一段重要的时期。

An argument from economy is not a proof. But the bigger point is that the evidence for many lineages and admixtures should have the effect of shaking our confidence in what to many people is now an unquestioned assumption that Africa has been the epicenter of all major events in human evolution. Based on the skeletal record, it is certain that Africa played a central role in the evolution of our lineage prior to two million years ago, as we have known ever since the discovery of the upright walking apes who lived in Africa millions of years before Homo. We know too that Africa has played a central role in the origin of anatomically modern humans, based on the skeletons of humans with anatomically modern features there up to around three hundred thousand years ago, and the genetic evidence for a dispersal in the last fifty thousand years out of Africa and the Near East. But what of the intervening period between two million years ago and about three hundred thousand years ago? In a large part of this time, the human skeletons we have from Africa are not obviously more closely related to modern humans than are the human skeletons of Eurasia.²⁵ Over the last couple of decades, there has been a pendulum swing toward the view that because our lineage was in Africa before two million years ago and after three hundred thousand years ago, our ancestors must always have been there. But Eurasia is a rich and varied supercontinent, and there is no fundamental reason that the lineage leading to modern humans cannot have sojourned there for an important period before returning to Africa.

基因证据表明，现代人类的祖先可能在其进化史上相当长的一段时间都生活在欧亚大陆，这一观点实际上与玛丽亚·马丁农-托雷斯和罗宾·丹内尔提出的理论相符。 ²⁶他们的观点在考古学和人类学领域属于少数派，但却备受尊重。他们认为，在西班牙阿塔普埃尔卡发现的、距今约一百万年的人类化石（他们称之为“先驱人”）展现出多种特征，表明他们来自一个现代人类和尼安德特人的共同祖先群体。对于一个在欧亚大陆存在现代人类/尼安德特人共同祖先群体的群体而言，这是一个非常古老的年代。许多人认为欧洲的尼安德特人起源于非洲以外的地区。祖先群体的辐射演化假设两个群体的祖先当时都生活在非洲。结合这一证据和对石器类型的考古分析，马丁农-托雷斯和丹内尔认为，欧亚大陆可能从至少140万年前一直持续有人居住，直到80万年前人类和尼安德特人的最近共同祖先出现。此时，其中一个谱系迁徙回非洲，最终演化成现代人类。 ²⁷新的遗传证据使马丁农-托雷斯和丹内尔的理论更具说服力。

The genetic evidence that the ancestors of modern humans may have spent a substantial part of their evolutionary history in Eurasia is in fact consistent with a theory advanced by María Martinón-Torres and Robin Dennell.²⁶ Theirs is a minority viewpoint within the fields of archaeology and anthropology, but a respected one. They argue that humans they call Homo antecessor, found in Atapuerca, Spain, and dating to around one million years ago, show a mix of traits indicating that they are from a population ancestral to modern humans and Neanderthals. This is a very ancient date for a modern human/Neanderthal ancestral population to exist in Eurasia. Many who think that Neanderthals in Europe descend from an out-of-Africa radiation of an ancestral population would assume that the ancestors of both populations were still in Africa at that time. Combining this evidence with archaeological analysis of stone tool types, Martinón-Torres and Dennell argue for the possibility of continuous Eurasian habitation from at least 1.4 million years ago until the most recent common ancestor of humans and Neanderthals after eight hundred thousand years ago, at which point one lineage migrated back to Africa to become the lineage that evolved into modern humans.²⁷ The Martinón-Torres and Dennell theory becomes more plausible in light of the new genetic evidence.

“走出非洲”理论的魅力之一在于其简化的观点，即非洲——尤其是东非——一直是人类多样性的摇篮和创新发生的地方，而世界其他地区则是一个进化停滞的容器。但人类进化的所有关键事件真的都发生在同一个地区吗？基因数据显示，许多古人类群体曾遍布欧亚大陆，其中一些群体还与现代人类杂交。这迫使我们质疑，为什么人类的迁徙方向总是从非洲向欧亚大陆，而有时是否也可能是相反的方向。

Part of the “out of Africa” allure is the simplifying idea that Africa—and especially East Africa—has always been the cradle of human diversity and the place where innovation occurred, and that the rest of the world is an evolutionarily inert receptacle. But is there really such a strong case that all the key events in human evolution happened in the same region of the world? The genetic data show that many groups of archaic humans populated Eurasia and that some of these interbred with modern humans. This forces us to question why the direction of migration would have always been out of Africa and into Eurasia, and whether it could sometimes have been the other way around.

迄今为止最古老的DNA

The Most Ancient DNA Yet

2014年初，马蒂亚斯·迈耶、斯万特·帕博及其莱比锡的同事们将已知最古老的人类DNA记录延长了约四倍。他们对来自西班牙西玛·德洛斯·韦索斯洞穴系统的一具距今超过40万年的海德堡人（Homo heidelbergensis）个体的线粒体DNA进行了测序。该洞穴系统位于一个13米深的竖井底部，共发现了28具古代人类遗骸。 ²⁸西玛洞穴的骨骼具有早期尼安德特人的特征，挖掘这些骨骼的考古学家认为，它们是现代人类祖先分化后，演化成尼安德特人的谱系的一部分。迈耶和帕博发表线粒体DNA测序结果两年后，研究人员对这一发现进行了进一步的研究。他们利用来自西玛德洛斯韦索斯（Sima de los Huesos）的数据，发表了全基因组数据。²⁹他们的分析不仅证实了西玛人属于尼安德特人谱系，而且进一步表明，西玛人与尼安德特人的亲缘关系比与丹尼索瓦人的亲缘关系更近。这些结果直接证明，尼安德特人的祖先至少在四十万年前就已在欧洲进化，并且尼安德特人和丹尼索瓦人的谱系分化在那时已经开始。

At the beginning of 2014, Matthias Meyer, Svante Pääbo, and their colleagues in Leipzig extended by a factor of around four the record for the oldest human DNA obtained, sequencing mitochondrial DNA from a more than four-hundred-thousand-year-old Homo heidelbergensis individual from the Sima de los Huesos cave system in Spain where twenty-eight ancient humans were found at the bottom of a thirteen-meter shaft.²⁸ The Sima skeletons have early Neanderthal-like traits, and the archaeologists who excavated them have interpreted them as being on the lineage leading to Neanderthals after the separation from the ancestors of modern humans. Two years after Meyer and Pääbo published mitochondrial DNA data from Sima de los Huesos, they published genome-wide data.²⁹ Their analysis not only confirmed that the Sima humans were on the Neanderthal lineage, but went further in showing that the Sima humans were more closely related to Neanderthals than they are to Denisovans. These results provided direct evidence that Neanderthal ancestors were already evolving in Europe at least four hundred thousand years ago, and that the separation of the Neanderthal and Denisovan lineages had already begun by that time.

但西玛的数据也令人费解：西玛的线粒体基因组与丹尼索瓦人的亲缘关系比与尼安德特人的亲缘关系更近，这与全基因组范围内其与尼安德特人亲缘关系最近的模式相悖。 ³⁰如果全基因组测量的平均亲缘关系与线粒体DNA中观察到的亲缘关系之间只有一处差异，或许还可以认为这只是统计波动。但实际上，遗传关系中存在两处差异：一是西玛·德·洛斯·韦索斯个体虽然在其他基因组区域与尼安德特人亲缘关系更近，但其线粒体DNA却具有丹尼索瓦人的特征；二是西伯利亚丹尼索瓦个体虽然在其他基因组区域与尼安德特人亲缘关系更近，但其线粒体DNA与现代人类和尼安德特人的亲缘关系差异却是两者之间亲缘关系差异的两倍。³¹这两个观察结果同时出现的概率如此之低，似乎更有可能背后隐藏着更深层次的故事。

But the Sima data were also perplexing: Sima’s mitochondrial genome was more closely related to Denisovans than to Neanderthals, at odds with the genome-wide pattern of it being most closely related to Neanderthals.³⁰ If there were only one discrepancy between the average relationship measured by the whole genome and the relationship seen in mitochondrial DNA, it might just be possible to believe that this was a statistical fluctuation. But there are two discrepancies in the genetic relationships: the fact that the Sima de los Huesos individual has Denisovan-type mitochondrial DNA despite being closer to Neanderthals in the rest of the genome, and the fact that the Siberian Denisovan individual has mitochondrial DNA twice as divergent from modern humans and Neanderthals as they were from each other despite being closer to Neanderthals in the rest of the genome.³¹ The coincidence of these two observations is so improbable that it seems more likely that there is a deeper story to unravel.

或许，与丹尼索瓦人杂交的超古人类在欧亚大陆人类历史上扮演的角色远比我们最初想象的要重要得多。或许，在大约140万至90万年前与现代人类的谱系分离后，这些超古人类扩散到欧亚大陆各地，并开始演化出丹尼索瓦人和西玛人身上发现的古老线粒体谱系。大约在同一时期的一半时间，另一群人可能也从现代人类的谱系中分离出来，并扩散到欧亚大陆各地。这群人可能与超古人类混血，为演化成尼安德特人的西部人群贡献了最大的祖先成分，并为演化成丹尼索瓦人祖先的东部人群贡献了较小但仍然相当可观的祖先成分。这种假设可以解释不同人群中两种远古分化的线粒体DNA类型的发现。它还可以解释我一个尚未发表的奇怪观察结果：在研究现代人类基因组与丹尼索瓦人和尼安德特人基因组共同遗传祖先的演化时间差异时，我未能找到任何证据表明存在一个超古老人群，该人群对丹尼索瓦人有贡献，但对尼安德特人没有贡献。相反，这些模式表明，丹尼索瓦人和尼安德特人都拥有来自同一超古老人群的祖先，只是丹尼索瓦人所占比例更高。

Perhaps the superarchaic humans—the ones who interbred with Denisovans—were a much more important part of Eurasian human population history than we initially imagined. Maybe, after separating from the lineage leading to modern humans around 1.4 to 0.9 million years ago, these superarchaic humans spread across Eurasia and began to evolve the ancient mitochondrial lineage found in the Denisovans and Sima humans. At roughly half this time, another group may have split off the lineage leading to modern humans and then spread throughout Eurasia. This group may have mixed into the superarchaic population, contributing the largest proportion of ancestry to populations in the west that evolved into Neanderthals, and a smaller but still substantial proportion of ancestry to populations in the east that became the ancestors of Denisovans. This scenario would explain the findings of two anciently divergent mitochondrial DNA types in the different groups. It could also explain an odd unpublished observation I have: that in studying the variation in the time since the common genetic ancestor of modern human genomes with both Denisovan and Neanderthal genomes, I have not been able to find evidence for a superarchaic population that contributed to Denisovans but not to Neanderthals. Instead the patterns suggest that Denisovans and Neanderthals both had ancestry from the same superarchaic population, with just a larger proportion present in the Denisovans.

约翰内斯·克劳斯及其同事提出了另一种理论。克劳斯认为，几十万年前，早期现代人类群体迁徙出非洲，并与西玛德洛斯韦索斯遗址的居民等群体融合，他们的线粒体DNA以及部分其他基因组被替换，从而形成了一个混合群体，最终演化成真正的尼安德特人。 ³²这一理论看似复杂，但实际上可以解释许多看似矛盾的观察结果，例如尼安德特人的线粒体序列比西玛德洛斯韦索斯遗址的个体或西伯利亚丹尼索瓦人的线粒体序列更接近现代人类这一事实。这或许可以解释这样一个事实：根据线粒体DNA估算的人类和尼安德特人共同祖先的出现时间（47万至36万年前） ³³ ，与基于全基因组分析估算的这两个人群祖先分离的时间（77万至55万年前） ³⁴相比，反而更为近期。这或许也可以解释，尽管此类工具的最早证据出现于基因估算的尼安德特人和现代人类谱系分离时间之后数十万年，但尼安德特人和现代人类却都使用了复杂的中石器时代石器制造方法 ³⁵ 。塞尔吉·卡斯特拉诺和亚当·西佩尔领导的一项研究表明，早期现代人类谱系与尼安德特人的祖先之间存在高达2%的基因杂交，这使得上述理论更具说服力。³⁶如果克劳斯的理论是正确的，那么这可能是传播所有尼安德特人身上发现的线粒体 DNA 的谱系。

Johannes Krause and colleagues have suggested an alternative theory. Krause’s idea is that several hundred thousand years ago, an early modern human population migrated out of Africa and mixed with groups like the one that lived in Sima de los Huesos, replacing their mitochondrial DNA along with a bit of the rest of their genomes and creating a mixed population that evolved into true Neanderthals.³² The idea might seem complicated, but in fact it could explain multiple disparate observations beyond the fact that Neanderthals had a mitochondrial sequence much more similar to modern humans than it did to either the Sima de los Huesos individual or the Siberian Denisovan. It could account for the fact that the estimated date of the common ancestor of humans and Neanderthals in mitochondrial DNA (470,000 to 360,000 years ago)³³ is paradoxically more recent than the estimated date of separation of the ancestors of these two populations based on the analysis of the whole genome (770,000 to 550,000 years ago).³⁴ It could also explain how it was that Neanderthals and modern humans both used complex Middle Stone Age methods of manufacturing stone tools, even though the earliest evidence for this tool type is hundreds of thousands of years after the genetically estimated separation of the Neanderthals and modern human lineages.³⁵ The theory finally becomes more plausible in light of a study led by Sergi Castellano and Adam Siepel that suggested up to 2 percent interbreeding into the ancestors of Neanderthals from an early modern human lineage.³⁶ If Krause’s theory is right, this could have been the lineage that spread the mitochondrial DNA found in all Neanderthals.

无论这些模式的解释是什么，很明显我们有很多东西需要说明。还有更多值得学习的地方。五万年前的欧亚大陆是一个繁忙的时期，至少从180万年前开始，就有多个人类群体从非洲迁徙而来。这些群体分裂成姐妹群体，彼此分化，然后又与其他群体以及新迁徙而来的人群混合。这些群体中的大多数已经灭绝，至少在其“纯种”形态下是如此。我们早已从骨骼和考古学中了解到，在现代人类迁出非洲之前，欧亚大陆存在着令人印象深刻的人类多样性。然而，在提取和研究古代DNA之前，我们并不知道欧亚大陆是与非洲相媲美的人类进化中心。在此背景下，关于现代人类和尼安德特人在西欧亚大陆相遇时是否发生过杂交的激烈争论——最终已明确支持杂交事件的观点，并认为这些事件对当今数十亿人的生存做出了贡献——似乎仅仅是预演而已。欧洲是一个半岛，是欧亚大陆面积适中的一小部分。鉴于丹尼索瓦人和尼安德特人种类繁多——至少在三个相隔数十万年的群体（即西伯利亚丹尼索瓦人、澳大利亚丹尼索瓦人和尼安德特人）的 DNA 序列中已经发现了他们的踪迹——看待这些群体的正确方式是将他们视为一个松散相关的、高度进化的古人类家族的成员，他们居住在欧亚大陆的广大地区。

Whatever explains these patterns, it is clear that we have much more to learn. The period before fifty thousand years ago was a busy time in Eurasia, with multiple human populations arriving from Africa beginning at least 1.8 million years ago. These populations split into sister groups, diverged, and mixed again with each other and with new arrivals. Most of those groups have since gone extinct, at least in their “pure” forms. We have known for a while, from skeletons and archaeology, that there was some impressive human diversity prior to the migration of modern humans out of Africa. However, we did not know before ancient DNA was extracted and studied that Eurasia was a locus of human evolution that rivaled Africa. Against this background, the fierce debates about whether modern humans and Neanderthals interbred when they met in western Eurasia—which have been definitively resolved in favor of interbreeding events that made a contribution to billions of people living today—seem merely anticipatory. Europe is a peninsula, a modest-sized tip of Eurasia. Given the wide diversity of Denisovans and Neanderthals—already represented in DNA sequences from at least three populations separated from each other by hundreds of thousands of years, namely Siberian Denisovans, Australo-Denisovans, and Neanderthals—the right way to view these populations is as members of a loosely related family of highly evolved archaic humans who inhabited a vast region of Eurasia.

古DNA让我们得以窥探遥远的过去，并迫使我们重新审视对过去的认知。如果说2010年发表的首个尼安德特人基因组打开了通往远古知识的闸门，那么丹尼索瓦人基因组以及随后的古DNA发现则如同打开了洪水闸门，涌现出大量新发现，颠覆了我们以往许多习以为常的认知。而这仅仅是个开始。

Ancient DNA has allowed us to peer deep into time, and forced us to question our understanding of the past. If the first Neanderthal genome published in 2010 opened a sluice in the dam of knowledge about the deep past, the Denisova genome and subsequent ancient DNA discoveries opened the floodgates, producing a torrent of findings that have disrupted many of the comfortable understandings we had before. And that was only the beginning.

第二部分

Part II

我们是如何走到

今天这一步的

How We Got to Where

We Are Today

4

4

 

 

人类的幽灵

Humanity’s Ghosts

古代北欧亚人的发现

The Discovery of the Ancient North Eurasians

面对生命的多样性，进化生物学家常常会用树来作比喻。查尔斯·达尔文在进化生物学的开端写道：“同一类生物之间的亲缘关系有时可以用一棵大树来表示……绿色的嫩芽可以代表现有的物种……树枝分叉成粗壮的大枝，大枝又分叉成越来越细小的枝，而这些大枝本身，在树还很小的时候，也曾是萌芽的嫩芽。” ^¹现存的种群是由过去的种群演化而来，而过去的种群则起源于非洲的共同根源。如果树的比喻是正确的，那么今天任何一个种群在过去的每个时期都只有一个共同的祖先种群。这棵树的意义在于，一旦一个种群分离，它就不会再重新融合，因为分支之间无法融合。

When confronted with the diversity of life, evolutionary biologists are drawn to the metaphor of a tree. Charles Darwin, at the inception of the field, wrote: “The affinities of all the beings of the same class have sometimes been represented by a great tree….The green and budding twigs may represent existing species….The limbs divided into great branches, and these into lesser and lesser branches, were themselves once, when the tree was small, budding twigs.”¹ Present populations budded from past ones, which branched from a common root in Africa. If the tree metaphor is right, then any population today will have a single ancestral population at each point in the past. The significance of the tree is that once a population separates, it does not remix, as fusions of branches cannot occur.

基因组革命之后涌现的大量新数据表明，用树状图来概括现代人类群体之间的关系是多么的不准确。我最亲密的合作者，应用数学家尼克·帕特森（Nick Patterson）开发了一系列正式的检验方法，用于评估树状模型是否能准确概括真实的群体关系。其中最重要的是四群体检验（Four Population Test），正如第一部分所述，该检验会检查基因组上数十万个个体差异位点——例如，有些人携带腺嘌呤（DNA的四种核酸或“字母”之一），而另一些人则携带其他氨基酸。含有鸟嘌呤——反映了很久以前发生的一次突变。如果用一棵树来描述四个种群，那么它们的突变频率预计会呈现简单的关系^。2

The avalanche of new data that has become available in the wake of the genome revolution has shown just how wrong the tree metaphor is for summarizing the relationship among modern human populations. My closest collaborator, the applied mathematician Nick Patterson, developed a series of formal tests to evaluate whether a tree model is an accurate summary of real population relationships. Foremost among these was the Four Population Test, which, as described in part I, examines hundreds of thousands of positions on the genome where individuals vary—for example, where some people have an adenine (one of the four nucleic acids or “letters” of DNA) and others have a guanine—reflecting a mutation that occurred deep in the past. If a set of four populations is described by a tree, then the frequencies of their mutations are expected to have a simple relationship.²

检验进化树模型最自然的方法是测量两个我们假设源自同一分支的群体的基因组突变频率。如果进化树模型正确，那么这两个群体的突变频率自它们与另外两个亲缘关系更远的群体分离以来，其变化将是随机的，因此这两对群体之间的频率差异在统计学上是独立的。如果进化树模型错误，频率差异之间将存在相关性，这表明分支间可能存在基因混合。四群体检验是我们证明尼安德特人与非非洲人比与非洲人亲缘关系更近，从而证明尼安德特人与非非洲人之间存在杂交的关键。³^但关于古人类与现代人类杂交的发现只是四群体检验众多发现中的一小部分。

The most natural way to test the tree model is to measure the frequencies of mutations in the genomes of two populations that we hypothesize have split from the same branch. If a tree model is correct, the frequencies of mutations in the two populations will have changed randomly since their separation from the other two more distantly related populations, and so the frequency differences between these two pairs of populations will be statistically independent. If a tree model is wrong, there will be a correlation between the frequency differences, pointing to the likelihood of mixture between the branches. The Four Population Test was central to our demonstration that Neanderthals are more closely related to non-Africans than to Africans, and thus that there was interbreeding between Neanderthals and non-Africans.³ But findings about interbreeding between archaic and modern humans are only a small part of what has been discovered with Four Population Tests.

我的实验室运用四群体检验法取得的首个重大发现，源于我们对“美洲原住民和东亚人是姐妹群体”这一广为流传的观点的检验。该观点认为，美洲原住民和东亚人起源于同一共同祖先分支，而该分支更早地与欧洲人和撒哈拉以南非洲人的祖先分离。出乎意料的是，我们发现，在撒哈拉以南非洲人所不具备的突变位点上，欧洲人与美洲原住民的亲缘关系比与东亚人的亲缘关系更近。人们很容易认为这一现象可以用一个简单的解释来说明，例如美洲原住民在过去五百年间可能混有欧洲移民的血统。但我们在所有研究过的美洲原住民群体中都发现了同样的模式，包括那些我们能够证明没有欧洲血统的群体。美洲原住民和欧洲人起源于同一共同祖先分支，而该分支更早地与东亚人分离的假设也与数据相悖。标准的群体关系树状模型显然存在严重问题。

My laboratory’s first major discovery using the Four Population Test came when we tested the widely held view that Native Americans and East Asians are “sister populations” that descend from a common ancestral branch that separated earlier from the ancestors of Europeans and sub-Saharan Africans. To our surprise, we found that at mutations not shared with sub-Saharan Africans, Europeans are more closely related to Native Americans than they are to East Asians. It would be tempting to argue that this observation has a trivial explanation, such as Native Americans having some ancestry from European migrants over the last five hundred years. But we found the same pattern in every Native American population we studied, including those we could prove had no European admixture. The scenario of Native Americans and Europeans descending from a common population that split earlier from East Asians was also contradicted by the data. Something was deeply wrong with the standard tree model of population relationships.

我们撰写了一篇论文来描述这些结果，并指出这些模式反映了美洲原住民祖先深处的一次混血事件：与欧洲人有亲缘关系的人们聚集在一起。在跨越连接亚洲和美洲的白令陆桥之前，与东亚人有亲缘关系的人群。我们于2009年提交了这篇题为《美洲原住民祖先的古代混血》的论文。论文被接受，但需要进行一些小的修改。然而，最终我们并未发表这篇论文。

We wrote a paper describing these results, suggesting that the patterns reflect an episode of mixture deep in the ancestry of Native Americans: a coming together of people related to Europeans and people related to East Asians prior to crossing the Bering land bridge between Asia and the Americas. We submitted this paper, “Ancient Mixture in the Ancestry of Native Americans,” in 2009. It was accepted pending minor revisions, but as it turns out, we never published it.

就在我们对那篇论文进行最后修改时，帕特森发现了一些更奇怪的事情，这让我们意识到我们只了解了故事的一部分。⁴^为了解释他的发现，我需要描述我们设计的另一个统计检验方法——三群体检验。该方法用于评估“测试”群体是否存在混合的证据。如果测试群体是由与比较群体存在两种不同关联的谱系混合而成——例如，非裔美国人是欧洲人和西非人的混合体——那么测试群体的突变频率预计会介于两个比较群体之间。相反，如果没有发生混合，就没有理由预期该群体的突变频率会处于中间水平。因此，混合与否会产生两种截然不同的模式。

Even as we were making our final revisions to that paper, Patterson discovered something even stranger, which made us realize we had understood only part of the story.⁴ To explain his discovery, I need to describe another statistical test we devised, the Three Population Test, which evaluates a “test” population for evidence of mixture. If the test population is a mixture of lineages related to the comparison populations in two different ways—as African Americans are a mixture of Europeans and West Africans—then the frequencies of the test population’s mutations are expected to be intermediate between those of the two comparison populations. In contrast, if mixture did not occur, there is no reason to expect the frequencies of mutations in the population to be intermediate. Thus the scenarios of mixture and no mixture yield two qualitatively very different patterns.

当我们对不同人群应用三群体检验时，发现当检验人群为北欧人时，统计结果为负值，这证明北欧人的祖先存在群体混合。我们尝试了来自全球五十多个人群的所有可能的比较群体组合，发现当一个比较群体为南欧人（尤其是撒丁岛人），另一个为美洲原住民时，群体混合的证据最为显著。显然，美洲原住民群体产生了最显著的负值，因为我们发现，当使用美洲原住民作为第二个比较群体时，统计结果比使用东亚人、西伯利亚人或新几内亚人时更为负面。我们的发现表明，北欧人（例如法国人）的祖先是多个群体混合的，其中一个群体与当今的美洲原住民的共同祖先比与任何其他现存人群的共同祖先更为丰富。

When we applied the Three Population Test to diverse human populations, we detected negative statistics when the test population was northern European, proving that population mixture occurred in the ancestors of northern Europeans. We tried all possible pairs of comparison populations from more than fifty worldwide populations and found that the mixture evidence was strongest when one comparison population was southern European, especially Sardinians, and the other was Native Americans. It was clearly Native American populations that produced the most negative values, as we found that the statistic was more negative when we used Native Americans for the second comparison population than when we used East Asians, Siberians, or New Guineans. What we had found was evidence that people in northern Europe, such as the French, are descended from a mixture of populations, one of which shared more ancestry with present-day Native Americans than with any other population living today.

我们如何理解三人口检验和四人口检验的结果？我们提出，一万五千多年前，曾有一个人口生活在……北欧亚大陆并非当今该地区居民的主要祖先。部分北欧亚大陆居民向东迁徙，穿越西伯利亚，融入了经由白令陆桥迁徙的人群，最终形成了美洲原住民。另一些人则向西迁徙，融入了欧洲人。这可以解释为什么如今，如果以美洲原住民作为祖先人群的代表，欧洲人的混血特征会非常明显；而以西伯利亚原住民作为祖先人群的代表，混血特征则不那么明显。西伯利亚原住民很可能是冰河时代后期从东亚南部迁徙到西伯利亚的人群的后裔。

How could we understand the results of both the Three Population Test and the Four Population Test? We proposed that more than fifteen thousand years ago, there was a population living in northern Eurasia that was not the primary ancestral population of the present-day inhabitants of the region. Some people from this population migrated east across Siberia and contributed to the population that crossed the Bering land bridge and gave rise to Native Americans. Others migrated west and contributed to Europeans. This would explain why today, the evidence of mixture in Europeans is strong when using Native Americans as a surrogate for the ancestral population and not as strong in indigenous Siberians, who plausibly descend from more recent, post–ice age migrations into Siberia from more southern parts of East Asia.

我们将这个新提出的族群称为“古代北欧亚人”。在我们提出这个族群时，他们就像一个“幽灵”——一个我们基于统计重建推断过去存在，但如今已不再以纯种形式存在的族群。如果古代北欧亚人生活在今天，他们无疑会被称为一个“种族”，因为我们可以证明，他们在基因上与当时所有其他欧亚人群的差异，与今天的“西欧亚人”、“美洲原住民”和“东亚人”彼此之间的差异大致相当。尽管他们没有留下纯种后代，但古代北欧亚人实际上取得了非凡的成功。如果我们把他们贡献给现代人群的所有遗传物质加起来，他们贡献的基因组数量高达数亿。总而言之，世界上超过一半的人口的基因组中有5%到40%源自古代北欧亚人。

We called this proposed new population the “Ancient North Eurasians.” At the time we proposed them, they were a “ghost”—a population that we can infer existed in the past based on statistical reconstruction but that no longer exists in unmixed form. The Ancient North Eurasians would without a doubt have been called a “race” had they lived today, as we could show that they must have been genetically about as differentiated from all other Eurasian populations who lived at the time as today’s “West Eurasians,” “Native Americans,” and “East Asians” are from one another. Although they have not left unmixed descendants, the Ancient North Eurasians have in fact been extraordinarily successful. If we put together all the genetic material that they have contributed to present-day populations, they account for literally hundreds of millions of genomes’ worth of people. All told, more than half the world’s population derives between 5 percent and 40 percent of their genomes from the Ancient North Eurasians.

古代北欧亚人的案例表明，虽然用树来比喻物种间的关系很贴切——因为物种间很少杂交，就像真正的树枝分叉后不会重新长在一起一样^⁵——但对于人类群体来说，这却是一个危险的比喻。基因组革命告诉我们，高度分化的群体之间曾多次发生大规模的混合^⁶ 。与其用树来比喻，不如用棚架来比喻，它象征着可以追溯到遥远过去的不断分叉和重组^{⁷ 。}

The case of the Ancient North Eurasians showed that while a tree is a good analogy for the relationships among species—because species rarely interbreed and so like real tree limbs are not expected to grow back together after they branch⁵—it is a dangerous analogy for human populations. The genome revolution has taught us that great mixtures of highly divergent populations have occurred repeatedly.⁶ Instead of a tree, a better metaphor may be a trellis, branching and remixing far back into the past.⁷

鬼魂被发现了

The Ghost Is Found

2013年底，埃斯克·威勒斯列夫及其同事发表了来自西伯利亚中南部马尔塔遗址一位男孩骨骼的全基因组数据，该男孩生活在大约两万四千年前。 ⁸马尔塔基因组与欧洲人和美洲原住民的遗传亲缘性最强，而与如今生活在该地区的西伯利亚人的亲缘性则弱得多——正如我们之前对古代北欧亚人“幽灵人口”的预测一样。马尔塔基因组如今已成为古代人类的原型样本。北欧亚人。古生物学家称之为“模式标本”，即科学文献中用来定义新发现类群的个体。

At the end of 2013, Eske Willerslev and his colleagues published genome-wide data from the bones of a boy who had lived at the Mal’ta site in south-central Siberia around twenty-four thousand years ago.⁸ The Mal’ta genome had its strongest genetic affinity to Europeans and Native Americans, and far less affinity to the Siberians who live in the region today—just as we had predicted for the ghost population of the Ancient North Eurasians. The Mal’ta genome has now become the prototype sample for the Ancient North Eurasians. Paleontologists would call it a “type specimen,” the individual used in the scientific literature to define a newly discovered group.

有了马尔塔基因组，其他拼图碎片也随之到位。我们不再需要从现代人群的数据中推断远古时期的历史。相反，通过直接从“幽灵人群”身上提取的基因组样本，我们得以了解数万年前的人口迁徙和混合情况，如同分析近代史一般。马尔塔基因组的发现，是我所知的古代DNA力量的最佳例证，它揭示了此前只能从现代数据中模糊感知的历史。

With the Mal’ta genome in hand, the other pieces of the puzzle snapped into place. It was no longer necessary to reconstruct from present-day populations what had happened long ago. Instead, with a genome sampled directly from the ghost population, it was possible to understand migrations and population admixtures from tens of thousands of years ago as if we were analyzing recent history. What became possible with the Mal’ta genome is the best example I know of the power of ancient DNA to uncover history that until then could only be dimly perceived from present-day data.

对马尔塔人基因组的分析清楚地表明，美洲原住民约三分之一的祖先来自古代北欧亚人，其余来自东亚人。正是这种主要的混合解释了为什么欧洲人在基因上与美洲原住民的亲缘关系比与东亚人的亲缘关系更近。我们之前未发表的手稿声称美洲原住民起源于东亚和西欧亚相关谱系的混合，这一说法是正确的，但这并非全部真相；这篇论文很快就被快速发展的古代DNA领域的新进展所掩盖。威勒斯列夫及其同事的发现远远超出了我们仅依赖现代人群所能达到的水平。威勒斯列夫团队不仅证明了美洲原住民起源于人群混合——这一点我们未能做到，因为我们无法排除其他可能性——而且他们还表明，这种混合只是更大故事的一部分。

The analysis of the Mal’ta genome made it clear that Native Americans derive about a third of their ancestry from the Ancient North Eurasians, and the remainder from East Asians. It is this major mixture that explains why Europeans are genetically closer to Native Americans than they are to East Asians. Our unpublished manuscript claiming that Native Americans descend from a mixture of East Asian and West Eurasian related lineages had been correct, but it was just not the whole story; the paper was overtaken by events in the fast-moving field of ancient DNA. What Willerslev and colleagues found went far beyond what we had been able to do by relying on only modern populations. The Willerslev team not only proved that Native Americans issued from population mixture—which we had not succeeded in doing as we could not rule out an alternative scenario—but they also showed that the mixture was part of a larger story.

发现如今非洲以外的几个主要人群都存在着高度混杂的基因，这与大多数科学家的预期截然相反。在基因组革命之前，我和大多数人一样，都认为我们今天看到的庞大的基因群体反映了过去人类的深刻分裂。但事实上，如今的这些庞大群体本身就是早期截然不同的人群混合的结果。此后，我们在分析过的所有人群中都发现了类似的模式：东亚人、南亚人、西非人、南部非洲人。人类历史上从未存在过单一的主干群体，而是自古以来就一直处于混杂状态。

The finding that several of the great populations outside of Africa today are profoundly mixed was at odds with what most scientists expected. Prior to the genome revolution, I, like most others, had assumed that the big genetic clusters of populations we see today reflect the deep splits of the past. But in fact the big clusters today are themselves the result of mixtures of very different populations that existed earlier. We have since detected similar patterns in every population we have analyzed: East Asians, South Asians, West Africans, southern Africans. There was never a single trunk population in the human past. It has been mixtures all the way down.

近东的幽灵

The Ghost of the Near East

2013 年全年，我实验室的 Iosif Lazaridis 都对一个没有古代 DNA 就无法理解的结果感到困扰。

Throughout 2013, Iosif Lazaridis in my laboratory was troubled by a result that could not be understood without ancient DNA.

拉扎里迪斯试图理解一项奇特的四群体测试结果，该结果显示，根据谱系树模型，东亚人、现代欧洲人和大约八千年前欧洲的狩猎采集者之间并无亲缘关系。然而，他的分析表明，现代东亚人在基因上平均而言与古代欧洲狩猎采集者的祖先更为接近，而非与现代欧洲人的祖先更为接近。在他之前，古代DNA研究已经表明，现代欧洲人的部分祖先来自近东的农民迁徙，而我之前一直认为这些农民与欧洲狩猎采集者源自同一祖先群体。拉扎里迪斯现在意识到，第一批欧洲农民的祖先与欧洲狩猎采集者的祖先在某些方面存在差异。事情远比这复杂得多。

Lazaridis was trying to understand a peculiar Four Population Test result showing that East Asians, present-day Europeans, and pre-farming European hunter-gatherers from around eight thousand years ago are not related to one another according to the tree model. Instead, his analysis showed that East Asians today are genetically more closely related on average to the ancestors of ancient European hunter-gatherers than they are to the ancestors of present Europeans. Ancient DNA studies prior to his work had already shown that present-day Europeans derive some of their ancestry from migrations of farmers from the Near East, who I had assumed were derived from the same ancestral population as European hunter-gatherers. Lazaridis now realized that the ancestry of the first European farmers was distinct from European hunter-gatherers in some way. Something more complicated was going on.

拉扎里迪斯权衡了两种可能的解释。一种解释是，古代欧洲狩猎采集者的祖先与古代东亚人之间存在基因混合，使得这两个群体在基因上有所关联。欧洲和东亚之间并不存在不可逾越的地理屏障，因此这种可能性很大。另一种解释是，早期欧洲农民为现代欧洲人贡献了大量的DNA，而他们的部分祖先则来自一个早期就从欧亚大陆主要居民群体中分离出来的群体。这样看来，东亚人与现代欧洲人的相似度，比他们与农业出现之前的欧洲狩猎采集者的相似度要低。

Lazaridis weighed two alternative explanations. One explanation was that there was mixture between the ancestors of ancient European hunter-gatherers and ancient East Asians, bringing these two populations together genetically. There are no insurmountable geographic barriers between Europe and East Asia, so this was a distinct possibility. The alternative explanation was that early European farmers who contributed much of the DNA to present-day Europeans derived some of their ancestry from a population that split early from the main group that peopled Eurasia. This would render East Asians less similar to present-day Europeans than they are to pre-farming European hunter-gatherers.

马尔塔的基因组序列公布后，拉扎里迪斯立即解决了这个问题。9他利用马尔塔的基因^组，对不同的四组人群进行了四群体检验。结果表明，马尔塔人和欧洲农业出现之前的狩猎采集者似乎都起源于一个共同的祖先群体，这个群体是在与东亚人和撒哈拉以南非洲人分离之后形成的。数据一致。用一棵简单的树状图来描述。但当拉扎里迪斯将统计数据中的古代欧洲狩猎采集者替换为现代欧洲人或早期欧洲农民时，这棵树状图的比喻就无法再描述这些数据了。现代欧洲人和近东人是混血的：他们的祖先来自一个不同的欧亚大陆谱系，该谱系在马耳他人、欧洲狩猎采集者和东亚人之间分化之前就已经存在。

Once the genome sequence from Mal’ta became available, Lazaridis instantly solved the problem.⁹ With Mal’ta in hand, he carried out Four Population Tests among various sets of four populations. Mal’ta and the pre-farming European hunter-gatherers appeared to descend from a common ancestral population that arose after the separation from East Asians and sub-Saharan Africans. The data were consistent with a simple tree. But when Lazaridis replaced ancient European hunter-gatherers in this statistic with either present-day Europeans or with early European farmers, the tree metaphor could no longer describe the data. Present-day Europeans and Near Easterners are mixed: they carry within them ancestry from a divergent Eurasian lineage that branched from Mal’ta, European hunter-gatherers, and East Asians before those three lineages separated from one another.

拉扎里迪斯将这一谱系称为“基础欧亚人”，以表明其在构成非非洲人群的谱系辐射演化中最深的分支位置。基础欧亚人是一个新的“幽灵人群”，其重要性堪比古代北欧亚人，这可以从他们留下的庞大后代基因组数量来衡量。如果这些人群之间存在简单的谱系关系，那么四群体检验的偏差值应为零。然而，该偏差值远大于预期值，这表明该“幽灵人群”贡献了现代欧洲人和近东人约四分之一的祖先成分。此外，它也为伊朗人和印度人贡献了相当比例的祖先成分。

Lazaridis called this lineage “Basal Eurasian” to denote its position as the deepest split in the radiation of lineages contributing to non-Africans. The Basal Eurasians were a new ghost population, one as important as the Ancient North Eurasians, measured by the sheer number of descendant genomes they have left behind. The extent of the deviations of the Four Population Test away from the value of zero that would be expected if the populations were related by a simple tree indicates that this ghost population contributed about a quarter of the ancestry of present-day Europeans and Near Easterners. It also contributed comparable proportions of ancestry to Iranians and Indians.

至今无人采集到欧亚大陆早期人群的古代DNA。找到这样的样本是目前古代DNA研究领域的圣杯之一，正如在马尔塔遗址发现之前寻找北欧古代人群的样本一样。但我们知道欧亚大陆早期人群确实存在。即使没有他们的古代DNA，我们也能根据他们遗留在我们已有数据的样本中的基因组片段，了解一些关于他们的重要信息。

No one has yet collected ancient DNA from the Basal Eurasians. Finding such a sample is at present one of the holy grails in the field of ancient DNA, just as finding the Ancient North Eurasians had been before the Mal’ta discovery. But we know that Basal Eurasians existed. And even without having their ancient DNA, we know important facts about them based on the genomic fragments they have left behind in samples for which we do have data.

与其他所有对现代非洲以外人群有贡献的谱系相比，基础欧亚人的一个显著特征是他们几乎不含尼安德特人血统。2016年，我们分析了近东地区的古代DNA，结果表明，生活在14000至10000年前的人们拥有约50%的基础欧亚人血统，大约是当今欧洲人这一比例的两倍。通过绘制基础欧亚人血统比例与尼安德特人血统比例的图表，我们发现，非非洲人的基础欧亚人血统越少，其尼安德特人血统就越多。因此，基础欧亚人血统为零的非非洲人，其尼安德特人DNA含量是基础欧亚人血统为50%的非非洲人的两倍。基础欧亚人血统百分比。由此推断，100%的基础欧亚人可能完全没有尼安德特人血统。^因此，无论尼安德特人混血发生在何处，似乎都主要发生在非非洲人种谱系的其他分支与基础欧亚人分离之后。

An extraordinary feature of the Basal Eurasians compared to all other lineages that have contributed to present-day people outside of Africa is that they harbored little or no Neanderthal ancestry. In 2016, we analyzed ancient DNA from the Near East to show that people who lived in the region fourteen thousand to ten thousand years ago had approximately 50 percent Basal Eurasian ancestry, about twice the proportion in Europeans today. Plotting the proportion of Basal Eurasian ancestry against the proportion of Neanderthal ancestry, we realized that the less Basal Eurasian ancestry a non-African person has, the more Neanderthal ancestry he or she has. Thus non-Africans who have zero percent Basal Eurasian ancestry have twice as much Neanderthal DNA as ones with 50 percent Basal Eurasian ancestry. By extrapolation, we might expect 100 percent Basal Eurasians to have no Neanderthal ancestry at all.¹⁰ So wherever the Neanderthal admixture occurred, it seems to have largely happened after the other branches of the non-African family tree separated from Basal Eurasians.

一个颇具吸引力的观点是，基础欧亚人代表了现代人类第二次迁徙到撒哈拉沙漠以北的后裔，这次迁徙发生在与尼安德特人杂交的人群扩散之后很久。然而，这种说法并不正确，因为基础欧亚人的谱系与其他非非洲人群有着许多共同的历史，包括他们都源自同一个相对较小的群体，这个群体在五万多年前建立了所有非非洲人群的谱系。基础欧亚人在欧亚大陆的古老存在，在考虑到生活在一万年前或更久远的今伊朗和以色列地区的人们，各自都拥有约50%的基础欧亚人血统时，就更加清晰了。 ¹¹尽管有明确的遗传证据表明，这两个群体在数万年间彼此隔离。¹²这表明，古代近东地区可能存在多个高度分化的基础欧亚人谱系共存，直到农业发展后，它们之间才开始出现大量的迁徙交流。欧亚大陆早期人群是人类遗传变异的主要且独特的来源，其中多个亚群体持续存在了很长时间。

A tempting idea is that the Basal Eurasians represent the descendants of a second wave of migration of modern humans north of the Sahara Desert, well after the dispersal of the population that interbred with Neanderthals. However, this is not correct, as the Basal Eurasian lineage shares much of the history of other non-Africans, including descent from the same relatively small population that founded all non-African lineages more than fifty thousand years ago. The ancient presence of the Basal Eurasians in Eurasia becomes even clearer when one considers that peoples who lived ten thousand years ago or more in what are now Iran and Israel each had around 50 percent Basal Eurasian ancestry,¹¹ despite the clear genetic evidence that these two populations had been isolated from one another for tens of thousands of years.¹² This suggests the possibility that there were multiple highly divergent Basal Eurasian lineages coexisting in the ancient Near East, not exchanging many migrants until farming expanded. The Basal Eurasians were a major and distinctive source of human genetic variation, with multiple subpopulations persisting for a long period of time.

原始欧亚人似乎与非洲以外的其他族群隔绝了数万年，那么他们究竟生活在哪里呢？由于缺乏古代DNA，我们只能进行推测。他们或许曾在北非生活过。由于撒哈拉沙漠的阻隔，北非与非洲大陆南部地区相距甚远，而且北非在生态上与西欧亚大陆联系更为紧密。如今，北非居民的祖先大多来自西欧亚大陆的移民，这使得该地区深远的遗传历史难以辨识。^然而，考古研究揭示了当地可能与原始欧亚人相对应的古代文化。例如，自现代欧亚人与撒哈拉以南非洲的近亲分化以来，尼罗河谷就一直有人类居住。

Where could the Basal Eurasians have lived, isolated as they seem to have been for tens of thousands of years from other non-African lineages? In the absence of ancient DNA, we can only speculate. It is possible that they may have sojourned in North Africa, which is difficult to reach from southern parts of the African continent because of the barrier of the Sahara Desert, and which is more ecologically linked to West Eurasia. Today, the peoples of North Africa owe most of their ancestry to West Eurasian migrants, making the deep genetic past in that region difficult to discern.¹³ However, archaeological studies have revealed ancient cultures there that could potentially have corresponded to the Basal Eurasians. The Nile Valley, for example, has been occupied by humans for the entire period since present-day Eurasians diverged from their closest relatives in sub-Saharan Africa.

关于欧亚大陆早期人群可能起源地的线索来自纳图夫人。纳图夫人是生活在近东西南部、距今约14000年前的狩猎采集者。 ¹⁴他们是已知最早定居的人群——尽管是狩猎采集者，但他们并不像其他人群那样为了寻找食物而四处迁徙。在他们的后代成为成熟的农民之前，他们建造了大型石质建筑，并积极管理当地的野生植物。他们的头骨以及他们制作的石器与同时期北非人的形状相似，因此有人推测纳图夫人是从北非迁徙到近东的。 ¹⁵ 2016年，我的实验室发表了来自以色列的六位纳图夫人的古代DNA，我们发现他们与早期伊朗狩猎采集者一样，拥有近东地区最高的欧亚大陆早期人群血统比例。¹⁶然而，我们的古代DNA数据无法确定纳图夫人的祖先居住在哪里，因为我们目前还没有来自同时期或更早时期生活在北非、阿拉伯半岛或西南近东地区的其他人群的可比古代DNA数据。即使纳图夫人与北非之间存在基因联系，这也不是全部真相，因为它无法解释伊朗和高加索地区古代狩猎采集者和农民中同样高比例的欧亚大陆早期血统。

A hint about the possible homeland of the Basal Eurasians comes from the Natufians, hunter-gatherers who lived after around fourteen thousand years ago in the southwestern parts of the Near East.¹⁴ They were the first people known to have lived in permanent dwellings—they did not migrate from place to place searching for food despite being hunter-gatherers. They built large stone structures and actively managed local wild plants before their successors became full-fledged farmers. Their skulls as well as the stone tools they made are similar in shape to those of North Africans who lived around the same time, and it has been suggested on this basis that the Natufians migrated to the Near East from North Africa.¹⁵ In 2016, my laboratory published ancient DNA from six Natufians from Israel, and we found that they share with early Iranian hunter-gatherers the highest proportions of Basal Eurasian ancestry in the Near East.¹⁶ However, our ancient DNA data cannot determine where the ancestors of the Natufians lived, as we do not yet have comparable ancient DNA data from any other populations that lived at this time or earlier in North Africa, Arabia, or the southwestern Near East. And even if a genetic connection between Natufians and North Africa is established, it will not be the whole story, as it cannot explain the equally high proportions of Basal Eurasian ancestry in the ancient hunter-gatherers and farmers of Iran and the Caucasus.

早期欧洲人的幽灵

The Ghosts of Early Europeans

不断发现的大型“幽灵人群”——古代北欧亚人和基础欧亚人——似乎让人觉得古DNA研究没有必要，因为可以根据现代人群的数据预测“幽灵人群”的存在。但统计重建的能力终究有限。利用现代人群的数据，我们很难追溯到比最近一次混血事件更久远的过去。此外，由于人类的迁徙能力很强，我们无法根据后代基因组的分析来准确确定祖先人群的居住地。而古DNA研究则能帮助我们解决这个问题。然而，直接从这些“幽灵”中提取信息，可以进一步追溯到更久远的过去，揭示出比仅凭现代数据所能发现的更为古老的“幽灵”。马尔塔人基因组测序就是如此。我们最初是通过统计学方法发现了马尔塔人的基因组，但一旦获得了序列信息，我们就能够发现更为遥远的欧亚大陆早期人群。 ¹⁷

The discovery of one major ghost population after another—Ancient North Eurasians and Basal Eurasians—might make it seem as if ancient DNA is unnecessary, since the existence of ghosts can be predicted from modern populations. But statistical reconstruction can only go so far. With data from present-day people, it is difficult to probe further back in time than the most recent mixture event. Moreover, because humans are so mobile, it is impossible to determine with any confidence where ancestral populations lived based on analyses of the genomes of their descendants. With ancient DNA directly extracted from the ghosts, however, it is possible to project further back in time, revealing even more ancient ghosts than can be recovered from modern data alone. So it was when the Mal’ta genome was sequenced. We discovered the Mal’ta genome statistically, but once we had access to the sequence, we were able to discover the even more distant Basal Eurasians.¹⁷

2016年，潘多拉魔盒的盖子被彻底打开，一大群远古幽灵涌了出来。我的实验室收集了来自欧亚大陆51位古代现代人的全基因组数据，其中大部分来自欧洲，他们生活在距今4.5万至7千年之间。 ¹⁸这些样本涵盖了整个末次冰盛期——距今约2.5万至1.9万年前——当时冰川覆盖了欧洲北部和中部纬度地区，所有人类都生活在南部半岛的避难所中。在我们开展这项工作之前，只有少数遗骸提供了这一时期的遗传数据，而且从这些遗骸的分析中得出的结论是静态且单一的。但凭借我们所有的新数据，我们可以证明，在这段漫长的时间里，人口发生了反复的转变、更替、迁徙和混合。

In 2016, the lid of Pandora’s box opened wide, and a whole mob of ancient ghosts whirled out. My laboratory assembled genome-wide data from fifty-one ancient modern humans in Eurasia, most of them from Europe, who lived between forty-five thousand and seven thousand years ago.¹⁸ These samples spanned the entire period of the Last Glacial Maximum—which occurred between twenty-five thousand and nineteen thousand years ago—when glaciers covered the northern and middle latitudes of Europe so that all humans there lived in refuges in its southern peninsulas. Prior to our work, just a few remains provided genetic data from this period, and the picture that emerged from their analysis was static and monochromatic. But with all our new data, we could show that repeated population transformations, replacements, migrations, and mixtures had taken place over this vast stretch of time.

分析古代DNA数据时，通常的做法是将古代个体与现代个体进行比较，试图从现代视角了解过去。但我实验室的傅巧梅（音译）采用这种方法后，她的研究结果对这些古代狩猎采集者几乎没有提供任何线索。现代人类之间的差异与她研究的那个时期欧洲人类之间的差异几乎无关。傅巧梅需要从数据本身的角度来分析它们。为此，她首先将古代个体彼此进行比较。她将他们分为四个组，每个组包含许多在基因和考古测定年代上都相似的样本。现在，她只需要了解这些组之间的关系。此外，还有一些个体没有与其他任何组聚类，尤其是在最古老的个体中。

When analyzing ancient DNA data, the usual approach is to compare ancient individuals to present-day ones, trying to get bearings on the past from the perspective of the present. But when this was done by Qiaomei Fu in my laboratory, her results shed little light on these ancient hunter-gatherers. The differences among humans today are hardly relevant to those that existed in Europe at the time depths she was studying. Fu needed to confront the data on their own terms. To do this, she began by comparing the ancient individuals to one another. She grouped them in four clusters that contained many samples that were similar both genetically and with respect to their archaeologically determined dates. Now she only needed to understand the relationships among the clusters. There were also some individuals who did not cluster with any others, especially among the oldest individuals.

通过这种方式整理样本，傅女士能够将现代人类在西欧亚大陆最初三万五千年的历史分解为至少五个关键事件。

With her samples organized in this way, Fu was able to break down the story of the first thirty-five thousand years of modern humans in West Eurasia into at least five key events.

事件一是现代人类向西欧亚大陆的扩散，这在两个最古老的样本中得到了印证：一个是距今约4.5万年的个体，其腿骨在西伯利亚西部的一条河岸边被发现，当时正处于风化侵蚀之中；^另一个是距今约4万年的个体，其下颌骨在罗马尼亚的一个洞穴中被发现。^这两个个体与后来的欧洲狩猎采集者的亲缘关系，并不比与现代东亚人的亲缘关系更近。这一发现表明，他们是早期现代人类先驱群体的成员，这些群体最初繁荣发展，但其后代大多已经消失。这些先驱群体的存在清楚地表明，过去并非必然通往现在。人类历史充满了死胡同，我们不应期望过去生活在某个地方的人就是今天生活在那里的人的直系祖先。大约三万九千年前，意大利那不勒斯附近的一座超级火山喷发，估计向欧洲倾泻了三百立方公里的火山灰，将之前的考古层与之后的考古层分隔开来。 ²¹在这一层之上几乎没有发现尼安德特人的遗骸或工具，这表明火山造成的气候紊乱（可能导致多年寒冬）或许加剧了尼安德特人与现代人类的竞争，最终引发了一场危机，导致尼安德特人灭绝。但尼安德特人并非唯一面临危机的人类。大多数在火山灰层之下留下遗骸的现代人类考古文化，在火山灰层之上却没有任何遗迹。许多现代人类的消失与他们的尼安德特人同代人一样，都是戏剧性的。 ²²

Event One was the spread of modern humans into western Eurasia and is evident in the two most ancient samples, an approximately forty-five-thousand-year-old individual whose leg bone had been found eroding out of a riverbank in western Siberia,¹⁹ and an approximately forty-thousand-year-old individual whose lower jaw was found in a cave in Romania.²⁰ Both individuals were no more closely related to later European hunter-gatherers than they were to present-day East Asians. This finding showed that they were members of pioneer modern human populations that initially flourished but whose descendants largely disappeared. The existence of these pioneer populations makes it clear that the past is not an inevitable march toward the present. Human history is full of dead ends, and we should not expect the people who lived in any one place in the past to be the direct ancestors of those who live there today. Around thirty-nine thousand years ago, a supervolcano near present-day Naples in Italy dropped an estimated three hundred cubic kilometers of ash across Europe, separating archaeological layers preceding it from those that succeeded it.²¹ Almost no Neanderthal remains or tools are found above this layer, suggesting that the climate disruption produced by the volcano, which could have produced multiyear winters, may have compounded competition with modern humans to create a crisis that drove Neanderthals to extinction. But the Neanderthals were not the only ones in crisis. Most modern human archaeological cultures that left remains below the ash layer left none above it. Many modern humans disappeared as dramatically as their Neanderthal contemporaries.²²

事件二是欧洲所有后来狩猎采集者的祖先谱系的传播。傅氏的四项群体检验表明，来自东欧（今俄罗斯欧洲部分）的一位距今约3.7万年的个体23 和来自西欧（今比利时）的一位距今约3.5万年的个体24都属于一个群体，该群体对所有后来的欧洲人（包括今天的欧洲人）都有贡献。^傅氏还运用四项群体检验表明，在距今约3.7万年至1.4万年前的整个时期内，她分析的几乎所有欧洲个体都可以被很好地描述为源自同一个共同祖先。此前未曾与非欧洲人群混血的人群。考古学家发现，大约三万九千年前的火山爆发后，一种被称为奥瑞纳文化的现代人类文化在欧洲传播开来，并制造出一种石器工具，这种工具取代了此前存在的各种不同的石器制造风格。因此，遗传学和考古学证据都表明，早期现代人类先驱者曾多次独立迁徙到欧洲，其中一些人最终灭绝，并被更为同质化的人群和文化所取代。

Event Two was the spread of the lineage that gave rise to all later hunter-gatherers in Europe. Fu’s Four Population Tests showed that both an approximately thirty-seven-thousand-year-old individual from eastern Europe (present-day European Russia)²³ and an approximately thirty-five-thousand-year-old individual from western Europe (present-day Belgium) were part of a population that contributed to all later Europeans, including today’s.²⁴ Fu also used Four Population Tests to show that during the entire period from around thirty-seven thousand to around fourteen thousand years ago, almost all the individuals she analyzed from Europe could be rather well described as descending from a single common ancestral population that had not experienced mixture with non-European populations. Archaeologists have shown that after the volcanic eruption around thirty-nine thousand years ago, a modern human culture spread across Europe making stone tools of a type known as Aurignacian, and that this replaced the diverse stone toolmaking styles that existed before. Thus genetic and archaeological evidence both point to multiple independent migrations of early modern human pioneers into Europe, some of which went extinct and were replaced by a more homogeneous population and culture.

第三个事件是格拉维特文化的兴起。大约在三万三千年到两万两千年前，格拉维特文化统治了欧洲大部分地区。他们留下的物质遗存包括丰腴的女性雕像、乐器以及令人叹为观止的洞穴壁画。与之前的奥瑞纳文化相比，格拉维特文化的人们更加重视埋葬死者，因此，我们发现的格拉维特文化时期的骨骼数量远超奥瑞纳文化时期。我们从埋葬于今比利时、意大利、法国、德国和捷克共和国的格拉维特文化时期个体中提取了DNA。尽管他们的地理分布极其广泛，但他们的基因却非常相似。傅氏的分析表明，他们的大部分祖先都源自欧洲狩猎采集者的同一分支，与来自远东欧、距今三万七千年的个体相同。之后，他们向西迁徙，取代了与奥瑞纳文化工具相关的分支，后者体现在距今三万五千年的比利时个体身上。因此，与格拉维特文化兴起相关的器物风格变化是由新人群的迁徙所驱动的。

Event Three was the coming of the people who made Gravettian tools, who dominated most of Europe between around thirty-three thousand and twenty-two thousand years ago. The material remains they left behind include voluptuous female statuettes, as well as musical instruments and dazzling cave art. Compared to the people who made Aurignacian tools who came before them, the people who made Gravettian tools were much more deliberate about burying their dead, and as a result we have many more skeletons from this period than we do from the Aurignacian period. We extracted DNA from Gravettian-era individuals buried in present-day Belgium, Italy, France, Germany, and the Czech Republic. They were all genetically very similar despite their extraordinary geographic dispersal. Fu’s analysis indicated that most of their ancestry derived from the same sublineage of European hunter-gatherers as the thirty-seven-thousand-year-old individual from far eastern Europe, and that they then spread west, displacing the sublineage associated with Aurignacian tools and represented in the thirty-five-thousand-year-old Belgian individual. The changes in artifact styles associated with the rise of the Gravettian culture were thus driven by the spread of new people.

第四项发现的标志是一具来自今西班牙境内、距今约一万九千年的骨骼——这是已知最早与马格德林文化相关的个体之一。在接下来的五千年里，马格德林文化的人们离开了温暖的避难所，向东北方向迁徙，追逐着消退的冰盖，最终抵达了今天的法国和德国。这些数据再次印证了考古发现与基因发现之间的关联，记录了人类向中欧的扩散。他们并非格拉维特文化的直系后裔。还有一个令人惊讶的发现：与马格德林文化相关的个体的大部分祖先都来自比利时一位距今三万五千年的个体所代表的亚系。这位个体与奥瑞纳文化工具有关，但后来在同一地点出现的却是使用格拉维特文化工具的人，他们的DNA与欧洲其他与东欧起源的格拉维特文化相关的个体相似。这又是一个以混合形式对后世群体做出贡献的“幽灵族群”。奥瑞纳文化谱系并没有消亡，而是在冰河时代末期复兴之前，在某个地理区域（可能在西欧）延续了下来。

Event Four was heralded by a skeleton from present-day Spain dating to around nineteen thousand years ago—one of the first individuals known to be associated with the Magdalenian culture, whose members over the next five thousand years migrated to the northeast out of their warm-weather refuge, chasing the retreating ice sheets into present-day France and Germany. The data once again showed a correspondence between the archaeological culture and genetic discoveries, documenting the spread of people into central Europe who were not directly descended from the Gravettians who had preceded them. There was also a surprise: most of the ancestry of individuals associated with the Magdalenian culture came from the sublineage represented by the thirty-five-thousand-year-old individual from Belgium who was associated with Aurignacian tools but who was later succeeded at the same site by people who used Gravettian tools and carried DNA similar to others in Europe associated with that culture of eastern European origin. Here was yet another ghost population that contributed to later groups in mixed form. The Aurignacian lineage had not died out, but instead had persisted in some geographic pocket, possibly in western Europe, before its resurgence at the end of the ice age.

事件五发生在约一万四千年前，正值末次冰期后的第一个强升温期，这一重大气候变化被称为博林-阿勒罗德（Bølling-Allerød）。地质重建显示，当时延伸至今尼斯附近地中海沿岸的阿尔卑斯山冰川在持续约一万年将欧洲东西部分隔开来后，最终融化。来自东南欧（意大利半岛和巴尔干半岛）的动植物大量迁徙至西南欧。我们基于古代DNA数据进行的^四项群体测试表明，类似的情况也发生在人类身上。大约一万四千年前，一群狩猎采集者遍布欧洲，他们的祖先与之前的马格德林文化人群截然不同，他们很大程度上取代了后者。生活在三万七千年至一万四千年前的欧洲人，很可能都源自一个共同的祖先群体，该群体更早地与如今近东地区人群的祖先分离。但大约一万四千年前，西欧的狩猎采集者与今天的近东人之间的亲缘关系变得更加密切。这证明，大约在这一时期，近东和欧洲之间发生了新的人口迁徙。

Event Five happened around fourteen thousand years ago, during the first strong warming period after the last ice age, a major climatic change known as the Bølling-Allerød. Geological reconstructions reveal that at this time, the Alpine glacial wall that extended down to the Mediterranean Sea near present-day Nice finally melted after about ten thousand years of dividing the west and east of Europe. Plants and animals from southeastern Europe (the Italian and Balkan peninsulas) migrated in abundance into southwestern Europe.²⁵ Our Four Population Tests on our ancient DNA data showed that something similar happened with humans. After around fourteen thousand years ago, a group of hunter-gatherers spread across Europe with ancestry quite different from that of the people associated with the preceding Magdalenian culture, whom they largely displaced. Individuals living in Europe between thirty-seven thousand and fourteen thousand years ago were all plausibly descended from a common ancestral population that separated earlier from the ancestors of lineages represented in the Near East today. But after around fourteen thousand years ago, western European hunter-gatherers became much more closely related to present-day Near Easterners. This proved that new migration occurred between the Near East and Europe around this time.

我们目前还没有来自东南欧和近东地区一万四千年前的古代DNA样本。因此，我们只能推测这一时期的人口迁徙情况。那些在南欧度过冰河时代的人们……随着阿尔卑斯山冰川的融化，他们逐渐在整个欧洲大陆占据主导地位。26^或许这些人也向东扩张到了安纳托利亚，他们的后裔进一步扩散到近东，在农民通过反向迁徙将近东血统传播回欧洲的五千多年前，就将欧洲和近东的基因传承融合在了一起。

We do not yet have ancient DNA from the period before fourteen thousand years ago from southeastern Europe and the Near East. We can therefore only surmise population movements around this time. The people who had waited out the ice age in southern Europe became dominant across the entire European continent following the melting of the Alpine glacial wall.²⁶ Perhaps these same people also expanded east into Anatolia, and their descendants spread farther to the Near East, bringing together the genetic heritages of Europe and the Near East more than five thousand years before farmers spread Near Eastern ancestry back into Europe by migrating in the opposite direction.

现代西欧亚人的基因形成

The Genetic Formation of Present-Day West Eurasians

如今，横跨欧洲、近东和中亚大部分地区的西欧亚大陆各族人民在基因上高度相似。早在18世纪，学者们就认识到西欧亚大陆人群的体质相似性，并将他们归类为“高加索人种”，以区别于东亚的“蒙古人种”、撒哈拉以南非洲的“尼格罗人种”以及澳大利亚和新几内亚的“澳洲人种”。进入21世纪，全基因组数据的出现，使得对现代人类群体进行聚类分析的方法比体质特征更为有效。

Today, the peoples of West Eurasia—the vast region spanning Europe, the Near East, and much of central Asia—are genetically highly similar. The physical similarity of West Eurasian populations was recognized in the eighteenth century by scholars who classified the people of West Eurasia as “Caucasoids” to differentiate them from East Asian “Mongoloids,” sub-Saharan African “Negroids,” and “Australoids” of Australia and New Guinea. In the 2000s, whole-genome data emerged as a more powerful way to cluster present-day human populations than physical features.

全基因组数据最初似乎验证了一些旧的分类。衡量两个群体间遗传相似性的最常用方法是计算它们之间突变频率差异的平方，然后对基因组中数千个独立突变进行平均，从而得到一个精确的数值。以此方法衡量，西欧亚大陆内部各群体之间的相似度通常是西欧亚人与东亚人相似度的七倍左右。当突变频率绘制在地图上时，从欧洲大西洋沿岸到中亚草原，西欧亚大陆呈现出同质性。在中亚地区存在一个急剧的变化梯度，之后在东亚地区又到达另一个同质性区域。 ²⁷

The whole-genome data at first seem to validate some of the old categories. The most common way to measure the genetic similarity between two populations is by taking the square of the difference in mutation frequencies between them, and then averaging across thousands of independent mutations across the genome to get a precisely determined number. Measured in this way, populations within West Eurasia are typically around seven times more similar to one another than West Eurasians are to East Asians. When frequencies of mutations are plotted on a map, West Eurasia appears homogeneous, from the Atlantic façade of Europe to the steppes of central Asia. There is a sharp gradient of change in central Asia before another region of homogeneity is reached in East Asia.²⁷

当今的人口结构是如何从远古时期的人口结构演变而来的？我们和其他古代DNA实验室在2016年发现，现代西欧亚人口的形成是由粮食产品的传播推动的。农业起源于大约一万两千年前，地点在土耳其东南部和叙利亚北部。当地的狩猎采集者开始驯化许多动植物，包括小麦、大麦、黑麦、豌豆、牛、猪和羊，这些动植物至今仍被许多西欧亚大陆居民所依赖。大约九千年前，农业开始向西传播到今天的希腊，几乎同时开始向东传播，到达今天巴基斯坦境内的印度河流域。在欧洲，农业沿着地中海沿岸向西传播到西班牙，并沿着多瑙河谷向西北传播到德国，最终到达北部的斯堪的纳维亚半岛和西部的不列颠群岛——这些地区是这种经济模式能够实际应用的最极端的地方。

How did the present-day population structure emerge from the one that existed in the deep past? We and other ancient DNA laboratories found in 2016 that the formation of the present-day West Eurasian population was propelled by the spread of food producers. Farming began between twelve and eleven thousand years ago in southeastern Turkey and northern Syria, where local hunter-gatherers began domesticating most of the plants and animals many West Eurasians still depend upon today, including wheat, barley, rye, peas, cows, pigs, and sheep. After around nine thousand years ago, farming began spreading west to present-day Greece and roughly at the same time began spreading east, reaching the Indus Valley in present-day Pakistan. Within Europe, farming spread west along the Mediterranean coast to Spain, and northwest to Germany through the Danube River valley, until it reached Scandinavia in the north and the British Isles in the west—the most extreme places where this type of economy was practical.

直到2016年，由于近东温暖的气候会加速化学反应，从而加速DNA的降解，因此，从近东获取全基因组古代DNA以评估考古记录中的变化在多大程度上是由人口迁徙推动的，一直未能实现。然而，两项技术突破改变了这一现状。其中一项突破来自马蒂亚斯·迈耶（Matthias Meyer）开发的方法，该方法通过富集从古代骨骼中提取的DNA，来提取感兴趣的人类序列。 ²⁸这种方法使古代DNA分析的成本降低了近千倍，并使我们能够获取那些原本DNA含量过低而无法进行研究的样本。我们与迈耶合作，改进了这种方法，使其能够对大量样本进行全基因组分析。²⁹第二项突破是人们认识到，颅骨的内耳部分——即岩骨——保存的DNA密度远高于大多数其他骨骼部位，每毫克骨粉中的DNA含量可高达其他部位的100倍。在都柏林工作的人类学家罗恩·平哈西（Ron Pinhasi）发现，岩骨内的耳蜗（蜗牛状的听觉器官）蕴藏着丰富的DNA。2015年和2016年对岩骨进行的^古DNA分析取得了突破性进展，首次使人们能够从温暖的近东地区获取古DNA。

Until 2016, getting genome-wide ancient DNA from the Near East to assess the extent to which these changes in the archaeological record were propelled by movements of people had failed, as the warm climate of the Near East quickens chemical reactions, accelerating the rate of breakdown of DNA. However, two technical breakthroughs changed this. One came from a method developed by Matthias Meyer, which involved enriching DNA extracted from ancient bones for human sequences of interest.²⁸ This approach makes ancient DNA analysis up to one thousand times more cost-effective and gives access to samples that would otherwise provide too little DNA to study. Working together with Meyer, we adapted this method to make possible genome-wide analysis of large numbers of samples.²⁹ The second breakthrough was the recognition that the inner-ear part of the skull—known as the petrous bone—preserves a far higher density of DNA than most other skeletal parts, up to one hundred times more for each milligram of bone powder. Within the petrous bone, the anthropologist Ron Pinhasi, working in Dublin, showed that the mother lode of DNA is found in the cochlea, the snail-shaped organ of hearing.³⁰ Ancient DNA analysis of petrous bones in 2015 and 2016 broke through one barrier after another and made it possible for the first time to get ancient DNA from the warm Near East.

^{我们与皮纳西合作，从农业}发源地的大部分地区——近东的44位古代居民身上提取了古代DNA。31结果显示，大约一万年前，在农业开始传播之时，西欧亚大陆的人口结构远非我们今天所见的单一基因型。伊朗西部山区的农民可能是最早驯养山羊的人，他们的基因直接来源于之前的狩猎采集者。同样，如今以色列和约旦的第一批农民也大多是纳图夫人狩猎采集者的后裔。但这两个群体在基因上也存在显著差异。我们和另一个研究小组 ³²发现，近东西部（包括安纳托利亚和黎凡特在内的新月沃土）第一批农民与东部（伊朗）第一批农民之间的基因分化程度，与如今欧洲人和东亚人之间的分化程度大致相当。在近东，农业的扩张不仅像欧洲那样依靠人口迁徙，也得益于基因差异巨大的群体之间共同思想的传播。

Working with Pinhasi, we obtained ancient DNA from forty-four ancient Near Easterners across much of the geographic cradle of farming.³¹ The results revealed that around ten thousand years ago, at the time that farming was beginning to spread, the population structure of West Eurasia was far from the genetic monoculture we observe today. The farmers of the western mountains of Iran, who may have been the first to domesticate goats, were genetically directly derived from the hunter-gatherers who preceded them. Similarly, the first farmers of present-day Israel and Jordan were descended largely from the Natufian hunter-gatherers who preceded them. But these two populations were also very genetically different from each other. We and another research group³² found that the degree of genetic differentiation between the first farmers of the western part of the Near East (the Fertile Crescent, including Anatolia and the Levant) and the first farmers of the eastern part (Iran) was about as great as the differentiation between Europeans and East Asians today. In the Near East, the expansion of farming was accomplished not just by the movement of people, as happened in Europe, but also by the spread of common ideas across genetically very different groups.

一万年前近东地区人类群体的高度分化，是西欧亚大陆更广泛模式的一个具体例证。约瑟夫·拉扎里迪斯（Iosif Lazaridis）领导了这项研究，并记录了这一模式。他分析了我们的数据，发现大约一万年前，西欧亚大陆至少存在四个主要群体：新月沃土的农民、伊朗的农民、中欧和西欧的狩猎采集者以及东欧的狩猎采集者。所有这些群体之间的差异，正如今天欧洲人和东亚人之间的差异一样大。如果一万年前的学者们试图建立基于血统的种族分类，他们会将这些群体归类为“种族”，尽管如今这些群体中没有一个是以纯粹混血的形式存在的。

The high differentiation of human populations in the Near East ten thousand years ago was a specific instance of a broader pattern across the vast region of West Eurasia, documented by Iosif Lazaridis, who led the analysis. Analyzing our data, he found that about ten thousand years ago there were at least four major populations in West Eurasia—the farmers of the Fertile Crescent, the farmers of Iran, the hunter-gatherers of central and western Europe, and the hunter-gatherers of eastern Europe. All these populations differed from one another as much as Europeans differ from East Asians today. Scholars interested in trying to create ancestry-based racial classifications, had they lived ten thousand years ago, would have categorized these groups as “races,” even though none of these groups survives in unmixed form today.

受动植物驯化这一革命性技术的推动，近东的农民开始迁徙，并与邻近地区融合。这项技术能够支持比狩猎采集更高的人口密度。但与欧洲先前一些狩猎采集者扩张时期出现的情况不同，近东地区并没有出现一个群体取代其他群体并导致其灭绝的情况，而是所有扩张的群体都为后来的人口增长做出了贡献。如今土耳其境内的农民不断扩张。进入欧洲。如今以色列和约旦的农民向东非扩张，他们的基因传承在今天的埃塞俄比亚最为显著。与今天伊朗农民相关的群体则向印度以及黑海和里海以北的草原扩张。他们与当地居民融合，建立了以畜牧业为基础的新经济，使得农业革命得以传播到原本不适宜驯化作物的地区。不同的粮食生产群体之间也相互融合，这一过程在大约五千年前的青铜时代因技术发展而加速。这意味着，此前西欧亚大陆高度发达的基因亚结构在青铜时代崩塌，最终形成了如今极低的基因分化水平。这是一个非凡的例子，说明技术——在本例中指的是驯化——如何促进了同质化，不仅体现在文化上，也体现在基因上。这表明，我们这个时代工业革命和信息革命所发生的事情，在人类历史上并非独一无二。

Spurred by the revolutionary technology of plant and animal domestication, which could support much higher population densities than hunting and gathering, the farmers of the Near East began migrating and mixing with their neighbors. But instead of one group displacing all the others and pushing them to extinction, as had occurred in some of the previous spreads of hunter-gatherers in Europe, in the Near East all the expanding groups contributed to later populations. The farmers in present-day Turkey expanded into Europe. The farmers in present-day Israel and Jordan expanded into East Africa, and their genetic legacy is greatest in present-day Ethiopia. Farmers related to those in present-day Iran expanded into India as well as the steppe north of the Black and Caspian seas. They mixed with local populations there and established new economies based on herding that allowed the agricultural revolution to spread into parts of the world inhospitable to domesticated crops. The different food-producing populations also mixed with one another, a process that was accelerated by technological developments in the Bronze Age after around five thousand years ago. This meant that the high genetic substructure that had previously characterized West Eurasia collapsed into the present-day very low level of genetic differentiation by the Bronze Age. It is an extraordinary example of how technology—in this case, domestication—contributed to homogenization, not just culturally but genetically. It shows that what is happening with the Industrial Revolution and the information revolution in our own time is not unique in the history of our species.

这些截然不同的人群融合为今天的西欧亚人，这一点在典型的北欧人特征中体现得淋漓尽致：蓝眼睛、浅肤色和金发。对古代DNA数据的分析表明，大约八千年前西欧的狩猎采集者拥有蓝眼睛，但肤色和头发颜色较深，这种组合在今天已十分罕见。 ³³欧洲最早的农民大多拥有浅肤色、深色头发和棕色眼睛——因此，欧洲的浅肤色很大程度上要归功于迁徙的农民。³⁴已知最早的典型欧洲金发突变案例来自一万七千年前西伯利亚东部贝加尔湖地区的一位古代北欧亚人。³⁵如今在中欧和西欧存在的数亿个这种突变基因很可能源于一次大规模的迁徙，当时的人群拥有古代北欧亚人的血统，这一事件将在下一章中详细阐述。 ³⁶

The fusion of these highly different populations into today’s West Eurasians is vividly evident in what might be considered the classic northern European look: blue eyes, light skin, and blond hair. Analysis of ancient DNA data shows that western European hunter-gatherers around eight thousand years ago had blue eyes but dark skin and dark hair, a combination that is rare today.³³ The first farmers of Europe mostly had light skin but dark hair and brown eyes—thus light skin in Europe largely owes its origins to migrating farmers.³⁴ The earliest known example of the classic European blond hair mutation is in an Ancient North Eurasian from the Lake Baikal region of eastern Siberia from seventeen thousand years ago.³⁵ The hundreds of millions of copies of this mutation in central and western Europe today likely derive from a massive migration into the region of people bearing Ancient North Eurasian ancestry, an event that is related in the next chapter.³⁶

令人惊讶的是，古DNA革命通过发现幽灵人群及其混合的普遍性，正在推动一种对种族问题的批判。这种批判过去曾被学者提出，但由于缺乏硬科学的支持而从未受到重视。事实。37^通过证明一万至四千年前西欧亚大陆的基因断层线与今天的截然不同，古DNA革命表明，今天的分类并不能反映生物学的基本“纯粹”单元。相反，今天的划分是近期的现象，其起源于反复的混合和迁徙。古DNA革命的发现表明，混合还将继续。混合是我们存在的根本，我们需要接受它，而不是否认它的存在。

Surprisingly, the ancient DNA revolution, through its discovery of the pervasiveness of ghost populations and their mixture, is fueling a critique of race that has been raised by scholars in the past, but was never prominent because of a lack of support from hard scientific facts.³⁷ By demonstrating that the genetic fault lines in West Eurasia between ten thousand and four thousand years ago were entirely different from today’s, the ancient DNA revolution has shown that today’s classifications do not reflect fundamental “pure” units of biology. Instead, today’s divisions are recent phenomena, with their origin in repeating mixtures and migrations. The findings of the ancient DNA revolution suggest that the mixtures will continue. Mixture is fundamental to who we are, and we need to embrace it, not deny that it occurred.

5

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现代欧洲的形成

The Making of Modern Europe

奇怪的撒丁岛

Strange Sardinia

2009年，由约阿希姆·伯格（Joachim Burger）领导的遗传学家团队对古代欧洲狩猎采集者和一些最早的欧洲农民的线粒体DNA片段进行了测序。¹^虽然线粒体DNA比基因组的其他部分短数十万倍，但它具有足够的变异性，可以将世界各地的人们划分为不同的类型。几乎所有古代狩猎采集者都携带同一种线粒体DNA类型。但后来的农民携带的线粒体DNA类型仅占这些类型的几个百分点，而且他们的DNA与今天在南欧和近东地区发现的DNA更为相似。显然，这些农民并非欧洲狩猎采集者的后裔。

In 2009, geneticists led by Joachim Burger sequenced stretches of mitochondrial DNA from ancient European hunter-gatherers and some of the earliest farmers of Europe.¹ Although mitochondrial DNA is hundreds of thousands of times shorter than the rest of the genome, it has enough variation to allow categorization of the peoples of the world into distinct types. Nearly all ancient hunter-gatherers carried one set of mitochondrial DNA types. But the farmers who succeeded them carried no more than a few percent of those types, and their DNA was more similar to that seen today in southern Europe and the Near East. It was clear that the farmers came from a population that did not descend from European hunter-gatherers.

线粒体DNA只是基因组的一小部分，然而，随后的全基因组研究却得出了一些奇怪的结果。2012年，一个遗传学家团队对“冰人”的基因组进行了测序。“冰人”是一具自然形成的木乃伊，距今约5300年，于1991年在阿尔卑斯山融化的冰川上被发现。^严寒保存了他的遗体和随身物品，生动地展现了一个显然极其复杂的文明，其历史可以追溯到文字出现之前的数千年。他的皮肤上布满了数十处纹身。他身穿草编斗篷，脚蹬精缝鞋。他携带一把铜刃斧。他还带了一套生火工具。他肩膀上的箭头和撕裂的动脉表明他曾中枪，踉跄地爬到山顶后倒下。根据他牙釉质中锶、铅和氧的同位素分析，他很可能在附近的山谷长大，那里地下水、植物和当地岩石中的同位素比例与他所在的地区相似。³^但古代DNA数据显示，他最近的基因亲属并非现代阿尔卑斯山居民。相反，他最近的基因亲属是地中海撒丁岛的居民。

Mitochondrial DNA is only a small portion of the genome, however, and the whole-genome studies that followed delivered strange results. In 2012, a team of geneticists sequenced the genome of the “Iceman,” a natural mummy dating to approximately fifty-three hundred years ago that was discovered in 1991 on a melting glacier in the Alps.² The cold had preserved his body and equipment, providing a vivid snapshot of what obviously had been an extraordinarily complex culture dating to thousands of years before the arrival of writing. His skin was covered with dozens of tattoos. He wore a woven grass cloak and finely sewn shoes. He carried a copper-bladed axe and a kit for lighting fires. An arrowhead in his shoulder and a torn artery showed that he had been shot and had stumbled to the top of a mountain pass before collapsing. Based on the isotopes of the elements strontium, lead, and oxygen in the enamel capping his teeth, it seemed likely he had grown up in a nearby valley where isotopes (contained in groundwater and plants, and derived from the local rocks) had similar ratios.³ But the ancient DNA data showed that his closest genetic relatives are not present-day Alpine people. Instead, his closest relatives today are the people of Sardinia, an island in the Mediterranean Sea.

这种与现代撒丁岛人的奇特联系不断出现。就在冰人基因组发表的同一年，乌普萨拉大学的蓬图斯·斯科格伦德、马蒂亚斯·雅各布森及其同事发表了四份来自约五千年前生活在瑞典的个体的基因组序列。4 在^他们的研究之前，一种主流理论认为，当时的瑞典狩猎采集者是农民的后裔，他们为了开发波罗的海丰富的渔业资源而适应了狩猎采集的生活方式。他们并非直接源自几千年前生活在北欧（包括瑞典）的狩猎采集者。但古代DNA推翻了这一理论。农民和狩猎采集者之间的基因差异，非但没有接近，反而几乎与今天的欧洲人和东亚人之间的差异一样大。而且，农民与撒丁岛人之间再次出现了那种奇特的联系。

This strange link to present-day Sardinians kept turning up. In the same year that the Iceman’s genome was published, Pontus Skoglund, Mattias Jakobsson, and colleagues at the University of Uppsala published four genome sequences from individuals who lived about five thousand years ago in Sweden.⁴ A leading theory up until their study was that the Swedish hunter-gatherers who lived at that time descended from farmers who had adapted a hunter-gatherer lifestyle to exploit the rich fisheries of the Baltic Sea, and were not directly descended from the hunter-gatherers who had lived in northern Europe (including Sweden) several thousand years earlier. But ancient DNA disproved this theory. Instead of being genetically close to each other, the farmers and hunter-gatherers were almost as different from each other as Europeans are from East Asians today. And the farmers once again had that strange link to Sardinians.

斯科格伦德和雅各布森提出了一个新的模型来解释这些发现——祖先来自近东的迁徙农民在欧洲扩散，与沿途遇到的狩猎采集者几乎没有基因融合。这与此前流行的卢卡·卡瓦利-斯福尔扎的农业扩张模型形成鲜明对比。卡瓦利-斯福尔扎的模型强调扩张过程中与当地狩猎采集者广泛的基因融合和互动。⁵^新模型不仅可以解释大约五千年前瑞典狩猎采集者和农民之间显著的基因差异，还可以解释为什么古代农民的基因与今天的撒丁岛居民相似，而撒丁岛居民很可能是迁徙到该岛的农民的后裔。大约八千年前，这支迁徙队伍在很大程度上取代了之前的狩猎采集者。这些农民的后裔与世隔绝地生活在撒丁岛上，因此他们受后来改变欧洲大陆人口的人口变迁事件的影响甚微。到目前为止，一切似乎都很合理——这个新模型解释了大约五千年前大多数欧洲人的基因构成。但斯科格伦德和雅各布森更进一步提出，狩猎采集者和农民这两个群体可能贡献了当今欧洲人几乎所有的祖先。然而，他们在这里忽略了一个极其重要的因素。

Skoglund and Jakobsson proposed a new model to explain these findings—that migrating farmers whose ancestors originated in the Near East spread over Europe with little mixture with the hunter-gatherers they encountered along the way, a sharp contrast to Luca Cavalli-Sforza’s model for the farming expansion into Europe that had been popular until this time and that emphasized extensive mixture and interaction with the local hunter-gatherers during the expansion.⁵ The new model would not only explain the striking genetic contrast between hunter-gatherers and farmers in Sweden around five thousand years ago. It would also explain why the ancient farmers were genetically similar to present-day Sardinians, who plausibly descend from a migration of farmers to that island around eight thousand years ago that largely displaced the previous hunter-gatherers. Isolated on Sardinia, the descendants of these farmers were minimally affected by demographic events that later transformed the populations of mainland Europe. So far, so good— this new model explained the genetic composition of most Europeans up until around five thousand years ago. But Skoglund and Jakobsson also went further and proposed that these two sources—hunter-gatherers and farmers—might have contributed almost all the ancestry of Europeans living today. Here they missed something extraordinarily important.

地平线上的乌云

A Cloud on the Horizon

2012年，关于现代欧洲人口祖先来源这一重大问题似乎即将得到解答。但有一个观察结果却与此不符。

In 2012, it seemed that the big question of the ancestral sources of present-day European populations might be solved. But there was an observation that didn’t fit.

那一年，尼克·帕特森发表了他“三族群检验”中一个令人费解的结果。正如前一章所述，他发现如今北欧人的基因突变频率介于南欧人和美洲原住民之间。他假设，这些发现可以用一个“幽灵族群”——古代北欧亚人——的存在来解释。这个族群在一万五千多年前分布于北欧亚大陆，他们既是经由白令陆桥迁徙到美洲的人口的祖先，也是北欧人的祖先。 ⁶一年后，埃斯克·威勒斯列夫及其同事从西伯利亚获得了一份古代DNA样本，与预测的古代北欧亚人的DNA相符——这份样本来自马尔塔人，其骨骼年代可追溯到大约两万四千年前。 ⁷

In that year, Nick Patterson published a perplexing result from his Three Population Test. As described in the previous chapter, he showed that the frequencies of mutations in northern Europeans today tend to be intermediate between those of southern Europeans and Native Americans. He hypothesized that these findings could be explained by the existence of a “ghost population”—the Ancient North Eurasians—who were distributed across northern Eurasia more than fifteen thousand years ago and who contributed both to the population that migrated across the Bering land bridge to people the Americas and to northern Europeans.⁶ A year later, Eske Willerslev and colleagues obtained a sample of ancient DNA from Siberia that matched the predicted Ancient North Eurasians—the Mal’ta individual whose skeleton dated to around twenty-four thousand years ago.⁷

如何调和古代北欧亚人对现代北欧人血统的贡献，与古代DNA研究直接证明的欧洲本土狩猎采集者和来自安纳托利亚的移民农民的双向混合现象呢？随着我们和其他人的发现，事情变得更加扑朔迷离。研究人员从八千年前至五千年前的狩猎采集者和农民身上获得了更多古代DNA数据，发现这些数据符合双向混合模型，没有任何证据表明存在古代北欧亚人的血统。8后来一定发生了一些意义深远的^事情——一定有一批新的移民到来，带来了古代北欧亚人的血统，并改变了欧洲。

How could the finding of an Ancient North Eurasian contribution to present-day northern Europeans be reconciled with the two-way mixture of indigenous European hunter-gatherers and incoming farmers from Anatolia that had been directly demonstrated through ancient DNA studies? The plot became even thicker as we and others obtained additional ancient DNA data from hunter-gatherers and farmers between eight thousand and five thousand years ago and found that they fit the two-way mixture model without any evidence of Ancient North Eurasian ancestry.⁸ Something profound must have happened later—a new stream of migrants must have arrived, introducing Ancient North Eurasian ancestry and transforming Europe.

2014-2015年间，古代DNA研究领域，尤其是我的实验室，发表了来自德国、西班牙、匈牙利、远东欧草原以及安纳托利亚早期农民等两百多位古代欧洲人的数据。9^通过将这些古代个体与当今西欧亚人进行比较，我实验室的约瑟夫·拉扎里迪斯（Iosif Lazaridis）得以揭示古代北欧亚人血统在过去五千年间是如何进入欧洲的。

In 2014–15, the ancient DNA community and especially my own laboratory published data from more than two hundred ancient Europeans from Germany, Spain, Hungary, the steppe of far eastern Europe, and the first farmers from Anatolia.⁹ By comparing the ancient individuals to West Eurasian people living today, Iosif Lazaridis in my laboratory was able to figure out how it was that the Ancient North Eurasian ancestry entered Europe within the last five thousand years.

我们最初采用的是主成分分析法，这种方法可以识别出突变频率组合中哪些组合最能有效地发现样本间的差异。为此，我们受益于基因组上约六十万个变异位点的超高分辨率数据，这一数字比Cavalli-Sforza在其1994年出版的著作中分析的位点数量多出约一万倍。 ¹⁰ Cavalli-Sforza曾尝试通过将主成分值绘制在世界地图上来理解遗传变异的主成分概括，而我们则能做得更多。我们根据每个个体相对于两个主成分的位置，在地图上绘制了一个点。在我们获得的近八百名现代西欧亚人群的散点图中，出现了两条平行线：左侧几乎包含了所有欧洲人，右侧几乎包含了所有近东人，两者之间存在着明显的间隙。通过将所有古代样本置于同一地点，我们可以观察它们的位置随时间的变化，过去八千年的欧洲历史便在我们眼前徐徐展开，宛如一部延时视频，展现了现代欧洲人是如何从祖先与当今大多数欧洲人几乎没有相似之处的人群中形成的^。11

Our initial approach was to carry out a principal component analysis, which can identify combinations of mutation frequencies that are most efficient at finding differences among samples. In doing this, we benefited from our extraordinarily high resolution data from around six hundred thousand variable locations on the genome, around ten thousand times more locations than Cavalli-Sforza had been able to analyze in his 1994 book.¹⁰ While Cavalli-Sforza had tried to make sense of the principal component summaries of genetic variation by plotting their values onto a map of the world, we could do far more. We plotted a single dot for each individual depending on where he or she fell relative to the two principal components. On the scatterplot we obtained for close to eight hundred present-day West Eurasians, two parallel lines appeared: the left containing almost all Europeans, and the right containing almost all Near Easterners, with a striking gap in between. By placing all the ancient samples onto the same plot, we could watch their positions shift over time, and the last eight thousand years of European history unfurled before our eyes, offering a time-lapse video showing how present-day Europeans formed from populations that had little resemblance in their ancestry to most Europeans living today.¹¹

首先出现的是狩猎采集者，他们本身是过去三万五千年来一系列人口变迁的产物，正如上一章（最近一章）所述。其中最显著的事件是大约一万四千年前东南欧人口的大规模扩张，这导致许多先前定居于此的人口流离失所。 ¹²在主成分分析中，当时生活在欧洲的狩猎采集者沿着衡量欧洲与近东差异的轴线，位于现代欧洲人之后。这与他们的祖先构成现代欧洲人而非现代近东人的观点相符。

First came the hunter-gatherers, who themselves were the product of a series of population transformations over the previous thirty-five thousand years as described in the last chapter, the most recent of which was a massive expansion of people out of southeastern Europe by around fourteen thousand years ago that displaced much of the previously established population.¹² In principal component analysis, the hunter-gatherers who lived in Europe at this time fell beyond present-day Europeans along an axis measuring the difference between Europe and the Near East. This was consistent with their having contributed ancestry to present-day Europeans but not to present-day Near Easterners.

其次是第一批农民，他们生活在大约8800至4500年前的德国、西班牙、匈牙利和安纳托利亚。来自这些地方的古代农民在基因上与今天的撒丁岛人相似，这表明一支早期农民群体可能来自安纳托利亚，他们登陆希腊后向西扩散到伊比利亚半岛，向北扩散到德国，并保留了至少90%的来自该移民来源的DNA，这意味着他们与沿途遇到的狩猎采集者的基因混合程度很低。然而，进一步的研究表明，情况并非如此简单。我们还发现，生活在大约6000年前的希腊南部伯罗奔尼撒半岛的农民，其部分祖先可能来自安纳托利亚的另一个群体——这个群体比欧洲其他地区农民的祖先群体（可能是安纳托利亚西北部农民的祖先）更多地与伊朗相关。¹³欧洲最早的农业活动发生在伯罗奔尼撒半岛和附近的克里特岛，那里的人们不使用陶器。这使得一些考古学家怀疑他们是否来自不同的迁徙群体。14^我们的古代DNA与这种观点相符，并表明这一人群可能延续了数千年之久。

Second came the first farmers, who lived between about eighty-eight hundred and forty-five hundred years ago in Germany, Spain, Hungary, and Anatolia. Ancient farmers from all these places were genetically similar to present-day Sardinians, showing that a pioneer farmer population had landed in Greece probably from Anatolia, and then spread to Iberia in the west and Germany in the north, retaining at least 90 percent of their DNA from that immigrant source, which meant that they mixed minimally with the hunter-gatherers they encountered along the way. Further investigation, though, showed that it was not quite so simple. We also found that farmers from the Peloponnese in southern Greece who lived around six thousand years ago may have derived part of their ancestry from a different source population in Anatolia—a population that descended more from Iranian-related populations than was the case in the northwestern Anatolian farmers who were a likely source population for the rest of Europe’s farmers.¹³ The first farming in Europe was practiced in the Peloponnese and the nearby island of Crete by people who did not use pottery. This has led some archaeologists to wonder if they were from a different migration.¹⁴ Our ancient DNA is consistent with this idea, and suggests the possibility that this population held on for thousands of years.

第三，我们发现生活在六千年前至四千五百年前的农民群体中出现了一种新的发展趋势。在这些后期农民中，我们观察到大约20%的狩猎采集者血统比例有所增加，而早期农民则没有这种血统。这表明，尽管延迟了数千年，但先前定居的人群与新迁入者之间的基因混合已经开始。 ¹⁵

Third, we identified a new development in farmers living between six thousand and forty-five hundred years ago. In many of these later farmers, we observed a shift toward approximately 20 percent extra hunter-gatherer ancestry, not present in the early farmers, implying that genetic mixing between the previously established people and new arrivals had begun, albeit after a couple of thousand years’ delay.¹⁵

农业文化和狩猎采集文化是如何共存的？漏斗杯文化或许能提供一些线索，这种文化因其装饰精美的器皿而得名。在距今约六千三百年的墓葬中发现了陶器。漏斗杯文化兴起于波罗的海沿岸数百公里的一片地带，这片区域并未被第一批农民所触及，可能是因为他们的耕作方法并不适用于北欧的黏重土壤。得益于这片难以耕作的自然环境，以及波罗的海沿岸丰富的渔猎资源，北方的狩猎采集者们有超过一千年的时间来适应农业的挑战。他们从南方的邻居那里引进了家畜，后来又引进了农作物，但仍然保留了许多狩猎采集的生活方式。漏斗杯文化的人们也建造了巨石墓，这些集体墓葬由巨大的石头构成，需要数十人才能搬动。考古学家科林·伦弗鲁认为，巨石建筑可能直接反映了南方农民和由狩猎采集者转变为农民的群体之间的界限——一种宣示领土、区分不同民族和文化的方式。 ¹⁶基因数据或许也印证了这种互动，因为显然有源源不断的新移民融入了混血人群。大约在六千年到五千年前，北方的大部分基因库被农民血统所取代，正是这种少量狩猎采集者血统和大量安纳托利亚农民血统的混合——在一个保留了狩猎采集文化关键要素的人群中——造就了漏斗杯陶器使用者以及许多其他同时代欧洲人的特征。

How did the farming and hunter-gatherer cultures coexist? Hints come from the Funnel Beaker culture, which is named for decorated clay vessels in graves dated after about sixty-three hundred years ago. The Funnel Beaker culture arose in a belt of land a few hundred kilometers from the Baltic Sea, which was not reached by the first wave of farmers, probably because their methods were not optimized for the heavy soils of northern Europe. Protected by the stronghold of their difficult-to-farm environment, and sustained by the fish and game resources of Baltic Europe, the northern hunter-gatherers had more than a thousand years to adapt to the challenge of farming. They adopted domesticated animals, and later crops, from their southern neighbors, but kept many elements of their hunter-gathering ways. The people of the Funnel Beaker culture were among those who built megaliths, the collective burial tombs made of stones so large it would have taken dozens of people to move them. The archaeologist Colin Renfrew suggested that megalith building might be a direct reflection of this boundary between southern farmers and hunter-gatherers turned farmers—a way of laying claim to territory, of distinguishing one people and culture from others.¹⁶ The genetic data may bear witness to this interaction, as there was clearly a stream of new migrants into the mixed population. Between six thousand and five thousand years ago, most of the northern gene pool was overtaken by farmer ancestry, and it was this mixture of a modest amount of hunter-gatherer-related ancestry and a large amount of Anatolian farmer–related ancestry—in a population that retained key elements of hunter-gatherer culture—that characterized the Funnel Beaker potters and many other contemporary Europeans.

欧洲达到了一种新的平衡。未与外族通婚的狩猎采集者逐渐消失，仅在瑞典南部沿海岛屿等孤立地区苟延残喘。在东南欧，定居的农民群体发展出了当时已知社会阶层最为分明的社会，其仪式中女性扮演着核心角色，正如考古学家玛丽亚·金布塔斯所展示的那样——这与后来以男性为中心的仪式截然不同。 ¹⁷在遥远的英国，巨石建造者们正辛勤劳作，最终建成了世界上最伟大的人造纪念碑：巨石阵。巨石阵成为了全国性的朝圣地，来自英国各地的物品纷至沓来。像巨石阵的建造者一样，人们正在为他们的神灵建造宏伟的庙宇。他们为逝者建造陵墓，却不可能预料到，仅仅几百年后，他们的后代就会消失，他们的土地就会被外族侵占。古代DNA揭示了一个惊人的事实：仅仅五千年前，如今所有北欧人的祖先尚未到来。

Europe had reached a new equilibrium. The unmixed hunter-gatherers were disappearing, persisting only in isolated pockets like the islands off southern Sweden. In southeastern Europe, a settled farmer population had developed the most socially stratified societies known up until that time, and rituals that as the archaeologist Marija Gimbutas showed featured women in a central way—a far cry from the male-centered rituals that followed.¹⁷ In remote Britain, the megalith builders were hard at work on what developed into the greatest man-made monument the world had seen: the standing stones of Stonehenge, which became a national place of pilgrimage as reflected by goods brought from the far corners of Britain. People like those at Stonehenge were building great temples to their gods, and tombs for their dead, and could not have known that within a few hundred years their descendants would be gone and their lands overrun. The extraordinary fact that emerges from ancient DNA is that just five thousand years ago, the people who are now the primary ancestors of all extant northern Europeans had not yet arrived.

东潮

The Tide from the East

大草原从欧洲中部一直延伸到中国，绵延约八千公里。考古证据表明，五千年前，几乎没有人居住在远离草原河谷的地方，因为这些地区降雨量太少，无法发展农业，水源也太少，无法供养牲畜。欧洲人居住的草原地区是各种地方文化的混合体，每种文化都有其独特的陶器风格，零星分布在有水源的地方^。18

The grasslands of the steppe stretch about eight thousand kilometers from central Europe to China. Prior to five thousand years ago, the archaeological evidence indicates that almost no one lived far from the steppe river valleys, because in between these areas there was too little rain to support agriculture, and too few watering holes to support livestock. The European third of the steppe was a hodgepodge of local cultures, each with its own pottery style, spread thinly over the landscape in places where water could be found.¹⁸

这一切随着大约五千年前亚姆纳亚文化的兴起而改变。亚姆纳亚人的经济以牛羊养殖为基础。他们起源于草原及其周边地区的早期文化，并比之前的文明更有效地利用了草原资源。他们的足迹遍布广袤的区域，从欧洲的匈牙利一直延伸到中亚阿尔泰山脉的山麓，并在许多地方用一种更为统一的生活方式取代了之前分散的文化。

All this changed with the emergence of the Yamnaya culture around five thousand years ago, whose economy was based on sheep and cattle herding. The Yamnaya emerged from previous cultures of the steppe and its periphery and exploited the steppe resources far more effectively than their predecessors. They spread over a vast region, from Hungary in Europe to the foothills of the Altai Mountains in central Asia, and in many places replaced the disparate cultures that had preceded them with a more homogeneous way of life.

推动亚姆纳亚文明传播的发明之一是车轮，其地理起源已不可考，因为车轮一旦出现——至少在亚姆纳亚文明兴起前几百年——便如野火般迅速蔓延至整个欧亚大陆。亚姆纳亚人或许是从南方的邻居——位于黑海和里海之间的高加索地区的迈科普文化——那里引进了使用车轮的马车。对于迈科普文化，如同对欧亚大陆的许多其他文化一样，车轮至关重要。但对于草原上的亚姆纳亚人来说，车轮的重要性甚至更胜一筹，因为它催生了一种全新的经济和文化。通过将牲畜套在马车上，亚姆纳亚人可以运水和补给。他们驾驭着马匹进入开阔的草原，开发了以前难以到达的广袤土地。亚姆纳人还利用了另一项创新——马匹。马匹不久前在草原东部被驯化，由于骑手可以放牧比步行者多得多的牲畜，牧牛效率大大提高，亚姆纳人的生产力也因此大幅提升^。19

One of the inventions that drove the spread of the Yamnaya was the wheel, whose geographic origin is not known because once it appeared—at least a few hundred years before the rise of the Yamnaya—it spread across Eurasia like wildfire. Wagons using wheels may have been adopted by the Yamnaya from their neighbors to the south: the Maikop culture in the Caucasus region between the Black and Caspian seas. For the Maikop, as for many cultures across Eurasia, the wheel was profoundly important. But for the people of the steppe, it was if anything even more important, as it made possible an economy and culture that were entirely new. By hitching their animals to wagons, the Yamnaya could take water and supplies with them into the open steppe and exploit the vast lands that had previously been inaccessible. By taking advantage of another innovation—the horse, which had recently been domesticated in a more eastern part of the steppe, and which made cattle herding more efficient as a single rider could herd many times the number of animals than could be herded by a person on foot—the Yamnaya also became vastly more productive.¹⁹

始于亚姆纳王朝的深刻文化变革对许多草原考古学家来说显而易见。人类对草原土地利用强度的增加，与永久定居点的几乎完全消失同时发生——亚姆纳王朝留下的几乎所有遗迹都是墓葬，即被称为库尔干的巨大土堆。有时，人们会将马车和马匹与墓葬一同埋葬在库尔干中，这凸显了马匹在他们生活方式中的重要性。车轮和马匹的出现彻底改变了经济，最终导致了村落生活的消亡。人们过着迁徙的生活，居住在类似古代移动房屋的地方。

The profound transformation in culture that began with the Yamnaya is obvious to many archaeologists of the steppe. The increase in the intensity of the human use of the steppe lands coincided with a nearly complete disappearance of permanent settlements—almost all the structures that the Yamnaya left behind were graves, huge mounds of earth called kurgans. Sometimes people were buried in kurgans with wagons and horses, highlighting the importance of horses to their lifestyle. The wheel and horse so profoundly altered the economy that they led to the abandonment of village life. People lived on the move, in ancient versions of mobile homes.

在2015年古代DNA数据爆炸式增长之前，大多数考古学家都难以想象，与亚姆纳亚文化传播相关的基因变化竟能与考古学上的变化一样剧烈。即使是亚姆纳亚文化传播对欧亚大陆历史具有变革性意义这一观点的主要倡导者之一，考古学家大卫·安东尼也无法接受其传播是由大规模迁徙驱动的观点。相反，他提出亚姆纳亚文化的大部分特征是通过模仿和传教传播的^。20

Prior to the explosion of ancient DNA data in 2015, most archaeologists found it inconceivable that the genetic changes associated with the spread of the Yamnaya culture could be as dramatic as the archaeological changes. Even the archaeologist David Anthony, a leading proponent of the idea that the spread of Yamnaya culture was transformative in the history of Eurasia, could not bring himself to suggest that its spread was driven by mass migration. Instead, he proposed that most aspects of Yamnaya culture spread through imitation and proselytization.²⁰

但基因分析的结果却并非如此。我们实验室的约瑟夫·拉扎里迪斯（Iosif Lazaridis）领导的团队对亚姆纳亚人的DNA分析表明，他们拥有此前在中欧并不存在的祖先组合。亚姆纳亚人正是缺失的成分，他们携带的祖先正是早期欧洲农民和狩猎采集者所需要的，从而形成了如今欧洲人群所呈现的这种祖先混合体。 ²¹我们的古代DNA数据也让我们了解到亚姆纳亚人自身是如何从更早的人群演变而来的。从七千年前到五千年前，我们观察到有一群人持续涌入草原，他们的祖先可以追溯到南方——因为他们与古代和现代的亚美尼亚人有着基因上的亲缘关系。最终，伊朗人融入了亚姆纳亚文化，他们的祖先来自这两个地区的比例大致为1:1。22^一个合理的推测是，迁徙路线经由黑海和里海之间的高加索地峡。沃尔夫冈·哈克、约翰内斯·克劳泽及其同事提供的古代DNA数据显示，北高加索地区的人口拥有这种类型的祖先，这种祖先构成一直延续到亚姆纳亚文化之前的迈科普文化时期。

But the genetics showed otherwise. Our analysis of DNA from the Yamnaya—led by Iosif Lazaridis in my laboratory—showed that they harbored a combination of ancestries that did not previously exist in central Europe. The Yamnaya were the missing ingredient, carrying exactly the type of ancestry that needed to be added to early European farmers and hunter-gatherers to produce populations with the mixture of ancestries observed in Europe today.²¹ Our ancient DNA data also allowed us to learn how the Yamnaya themselves had formed from earlier populations. From seven thousand until five thousand years ago, we observed a steady influx into the steppe of a population whose ancestors traced their origin to the south—as it bore genetic affinity to ancient and present-day people of Armenia and Iran—eventually crystallizing in the Yamnaya, who were about a one-to-one ratio of ancestry from these two sources.²² A good guess is that the migration proceeded via the Caucasus isthmus between the Black and Caspian seas. Ancient DNA data produced by Wolfgang Haak, Johannes Krause, and their colleagues have shown that the populations of the northern Caucasus had ancestry of this type continuing up until the time of the Maikop culture, which just preceded the Yamnaya.

鉴于迈科普文化对亚姆纳亚文化的影响，迈科普文化或其前身高加索地区的居民对亚姆纳亚文化做出基因贡献的证据并不令人惊讶。迈科普人不仅将马车技术传授给了亚姆纳亚人，而且他们还是最早建造库尔干墓的民族，这种墓葬在之后的数千年里一直是草原文化的典型特征。此外，有研究表明迈科普商品深受南部美索不达米亚乌鲁克文明的影响，而乌鲁克文明金属资源匮乏，且与北方进行贸易往来，这体现在北高加索地区发现的乌鲁克商品中。因此，来自南方的伊朗和亚美尼亚血统渗透迈科普地区的现象也合情合理。 ²³无论是什么文化进程使得南方居民对人口产生了如此巨大的影响，一旦亚姆纳亚文化形成，他们的后裔便向四面八方扩张。 ²⁴

The evidence that people of the Maikop culture or the people who proceeded them in the Caucasus made a genetic contribution to the Yamnaya is not surprising in light of the cultural influence the Maikop had on the Yamnaya. Not only did the Maikop pass on to the Yamnaya their technology of carts, but they were also the first to build the kurgans that characterized the steppe cultures for thousands of years afterward. The penetration of Maikop lands by Iranian- and Armenian-related ancestry from the south is also plausible in light of studies showing that Maikop goods were heavily influenced by elements of the Uruk civilization of Mesopotamia to the south, which was poor in metal resources and engaged in trade and exchange with the north as reflected in Uruk goods found in settlements of the northern Caucasus.²³ Whatever cultural process allowed the people from the south to have such a demographic impact, once the Yamnaya formed, their descendants expanded in all directions.²⁴

草原如何来到中欧

How the Steppe Came to Central Europe

大约五千年前，草原民族传入中欧之前，当地居民的基因主要源自九千年前从安纳托利亚迁徙至欧洲的第一批农民，仅有少量来自与他们融合的欧洲本土狩猎采集者的血统。同样在五千年前，远东地区的亚姆纳亚人的基因结构则呈现出不同的血统混合：伊朗血统人群与东欧狩猎采集人群的比例大致相等。与亚姆纳亚人有关的欧洲农民和草原群体尚未形成。

On the eve of the arrival of steppe ancestry in central Europe around five thousand years ago, the genetic ancestry of the people who lived there was largely derived from the first farmers who had come into Europe from Anatolia beginning after nine thousand years ago, with a minority contribution from the indigenous European hunter-gatherers who mixed with them. In far eastern Europe also around five thousand years ago, the genetic structure of the Yamnaya reflected a different mixture of ancestries: an Iranian-related population along with an eastern European hunter-gatherer population, in approximately equal proportions. Populations that were mixes of European farmers and steppe groups related to the Yamnaya had not yet formed.

草原血统对中欧的基因影响体现在一群属于绳纹器文化的人群中。绳纹器文化因其陶罐上用绳子压印装饰而得名。大约从四千九百年前开始，绳纹器文化的典型器物开始在从瑞士到俄罗斯欧洲部分的广阔区域传播。古代DNA数据显示，正是从绳纹器文化开始，与现代欧洲人血统相似的人群首次出现在欧洲。我和尼克·帕特森、约瑟夫·拉扎里迪斯开发了新的统计方法，据此估算，在德国，与绳纹器陶罐一同下葬的人，^其祖先约四分之三来自与亚姆纳亚文化相关的群体，其余则来自与该地区早期居民——农民——相关的群体。草原血统一直延续至今，我们在北欧所有后来的考古文化以及所有现代北欧人身上都发现了这种血统。

The genetic impact of steppe ancestry on central Europe came in the form of peoples who were part of the ancient culture known to archaeologists as the Corded Ware, so named after its pots decorated by the impressing of twine into soft clay. Beginning around forty-nine hundred years ago, artifacts characteristic of the Corded Ware culture started spreading over a vast region, from Switzerland to European Russia. The ancient DNA data showed that beginning with the Corded Ware culture, individuals with ancestry similar to present-day Europeans first appeared in Europe.²⁵ Nick Patterson, Iosif Lazaridis, and I developed new statistical methods that allowed us to estimate that in Germany, people buried with Corded Ware pots derive about three-quarters of their ancestry from groups related to the Yamnaya and the rest from people related to the farmers who had been the previous inhabitants of that region. Steppe ancestry has endured, as we also found it in all subsequent archaeological cultures of northern Europe as well as in all present-day northern Europeans.

基因数据最终解决了考古学界关于绳纹器文化与亚姆纳亚文化之间联系的长期争论。两者有许多显著的相似之处，例如建造大型墓葬、大量利用马匹和畜牧业，以及以男性为中心的、崇尚暴力的文化，这体现在一些墓葬中出土的大型权杖（或锤斧）上。与此同时，两种文化之间也存在着深刻的差异，尤其体现在它们所制作的陶器类型上，绳纹器风格的重要元素借鉴了此前中欧的陶器风格。但基因研究表明，绳纹器文化与亚姆纳亚文化之间的联系反映了人口的大规模迁徙。至少从基因层面来看，绳纹器文化的创造者是亚姆纳亚文化向西延伸的结果。

The genetic data thus settled a long-standing debate in archaeology about linkages between the Corded Ware and the Yamnaya cultures. The two had many striking parallels, such as the construction of large burial mounds, the intensive exploitation of horses and herding, and a strikingly male-centered culture that celebrated violence, as reflected in the great maces (or hammer-axes) buried in some graves. At the same time, there were profound differences between the two cultures, notably the entirely different types of pottery that they made, with important elements of the Corded Ware style adapted from previous central European pottery styles. But the genetics showed that the connection between the Corded Ware culture and the Yamnaya culture reflected major movements of people. The makers of the Corded Ware culture were, at least in a genetic sense, a westward extension of the Yamnaya.

绳纹器文化反映了草原人口向中欧的大规模迁徙，这一发现并非仅仅是一项枯燥的学术成果，它具有重要的政治和历史意义。20世纪初，德国考古学家古斯塔夫·科西纳是最早提出这一观点的人之一。过去分布于广阔地理区域的文化可以通过其遗留器物的风格相似性来识别。科西纳更进一步，将考古学鉴定的文化等同于民族，并首创了利用物质文化的传播来追踪古代迁徙的理念，他称之为“聚落考古学” （siedlungsarchäologische Methode）。基于绳纹器文化地理分布与德语区重叠的现象，科西纳认为，当今德国人和日耳曼语族的文化根源在于绳纹器文化。在他的论文《东德边境：德国人的故土》中，他论证道，由于绳纹器文化涵盖了当时的波兰、捷克斯洛伐克和俄罗斯西部地区，因此德国人理应将这些地区视为自己的领土。 ²⁶

The discovery that the Corded Ware culture reflected a mass migration of people into central Europe from the steppe was not just a sterile academic finding. It had political and historical resonance. At the beginning of the twentieth century, the German archaeologist Gustaf Kossinna was among the first to articulate the idea that cultures of the past that were spread across large geographic regions could be recognized through similarities in style of the artifacts they left behind. He also went further in viewing archaeologically identified cultures as synonymous with peoples, and he originated the idea that the spread of material culture could be used to trace ancient migrations, an approach he called the siedlungsarchäologische Methode, or “Settlement Archaeology.” Based on the overlap of the geographic distribution of the Corded Ware culture with the places where German is spoken, Kossinna suggested that the cultural roots of the Germans and of Germanic languages today lay in the Corded Ware culture. In his essay “The Borderland of Eastern Germany: Home Territory of the Germans,” he argued that because the Corded Ware culture included the territories of Poland, Czechoslovakia, and western Russia of his day, it gave Germans the moral birthright to claim those regions as their own.²⁶

科西纳的思想被纳粹所接受。尽管他于1931年去世，早于纳粹掌权，但他的学术成果仍被纳粹用作宣传的依据，并为其对东部领土的主权主张辩护。 ²⁷科西纳认为，人口迁徙是考古记录变化的主要原因，这一观点也迎合了纳粹的种族主义世界观，因为人们很容易想象，人口迁徙是由某些民族天生的生物优势所驱动的。二战后，欧洲考古学家开始反思考古领域的政治化，并着手批判科西纳及其同事的论点，记录了物质文化的变迁并非源于人口迁徙，而是源于当地发明或模仿的案例。他们呼吁人们在用人口迁徙来解释考古记录的变化时务必格外谨慎。如今，考古学家普遍认为，人口迁徙只是解释过去文化变迁的众多因素之一。许多考古学家仍然认为，当一个遗址存在重大文化变迁的证据时，应该假定这些变化反映的是思想的交流或当地的创新，而不是人口的迁徙^。28

Kossinna’s ideas were embraced by the Nazis, and although he died in 1931, before they came to power, his scholarship was used as a basis for their propaganda and a justification for their claims to territories to the east.²⁷ Kossinna’s suggestion that migration was the primary explanation for changes in the archaeological record was also attractive to the Nazis because it played into their racist worldview, as it was easy to imagine that migrations had been propelled by innate biological superiority of some peoples over others. Following the Second World War, European archaeologists reacting to the politicization of their field began picking apart the arguments of Kossinna and his colleagues, documenting cases in which changes in material culture were brought about through local invention or imitation and not the spread of people. They urged extreme caution about invoking migration to explain changes in the archaeological record. Today, a common view among archaeologists is that migrations are only one of many explanations for past cultural change. Many archaeologists still argue that when there is evidence for major cultural change at a site, the working assumption should be that the changes reflect communication of ideas or local invention, not necessarily movements of people.²⁸

将绳纹器文化与迁徙放在一起讨论，尤其会敲响警钟，因为科西纳……纳粹试图利用绳纹器文化构建德国民族认同的基础。29 ²⁰¹⁵年，在我们即将完成论文投稿准备工作时，一位提供骨骼样本的德国考古学家给所有合著者写了一封信：“我们必须（！）避免……被拿来与古斯塔夫·科西纳所谓的‘定居考古学方法’相提并论！” 随后，他和几位作者退出了论文的作者行列。之后，我们修改了论文，着重阐述了科西纳的论点与我们研究结果之间的差异，即绳纹器文化起源于东方，并且与之相关的人群此前并未在中欧定居。

Discussions of the Corded Ware culture and migration in the same breath ring particularly loud alarm bells because of Kossinna’s and the Nazis’ attempt to use the Corded Ware culture to construct a basis for national German identity.²⁹ While we were in the final stages of preparing a paper for submission in 2015, one of the German archaeologists who contributed skeletal samples wrote a letter to all coauthors: “We must(!) avoid…being compared with the so called ‘siedlungsarchäologische Methode’ from Gustaf Kossinna!” He and several contributors then resigned as authors before we modified our paper to highlight differences between Kossinna’s thesis and our findings, namely that the Corded Ware culture came from the east and that the people associated with it had not been previously established in central Europe.

绳纹器文化是通过东方迁徙传播的正确理论，早在20世纪20年代就由科西纳的同代人、考古学家V·戈登·柴尔德提出 ^30。然而，二战后，随着人们对纳粹滥用考古学的强烈反应（这种反应表现为对任何迁徙说法的极端怀疑），这一观点也逐渐被人们所摒弃 ³¹ 。我们发现的亚姆纳文化与绳纹器文化之间的基因联系，展现了古代DNA的颠覆性力量。它可以证明过去人口的迁徙，而在这个案例中，它记录了一次规模空前的人口更替，这是任何现代考古学家，即使是最坚定的迁徙论支持者，都不敢提出的。草原遗传祖先与通过墓葬和文物被归类为绳纹器文化人群之间的关联，并非仅仅是一个假设，而是一个已被证实的既定事实。

The correct theory that the Corded Ware culture spread through a migration from the east had already been proposed in the 1920s by Kossinna’s contemporary, the archaeologist V. Gordon Childe,³⁰ although this idea too fell out of favor in the wake of the Second World War and the reaction to the abuse of archaeology by the Nazis, a reaction that took the form of extreme skepticism about any claims of migration.³¹ Our finding about the genetic link between the Yamnaya and the Corded Ware culture demonstrates the disruptive power of ancient DNA. It can prove past movements of people, and in this case has documented a magnitude of population replacement that no modern archaeologist, even the most ardent supporter of migrations, had dared to propose. The association between steppe genetic ancestry and people assigned to the Corded Ware archaeological culture through graves and artifacts is not simply a hypothesis. It is now a proven fact.

草原上人口密度低的牧羊人是如何取代中欧和西欧人口稠密的农民的呢？考古学家彼得·贝尔伍德认为，一旦欧洲形成了人口稠密的农业人口，其他迁入的群体几乎不可能对其人口构成威胁，因为他们的数量与已有的人口相比微不足道。 ³²以英国或莫卧儿王朝对印度的占领为例。这两个政权统治印度次大陆数百年，但几乎没有在如今的印度人身上留下任何痕迹。然而，古代DNA确凿地表明，大约在四千五百年前，欧洲发生了大规模的人口更替。

How was it that the low-population-density shepherds from the steppe were able to displace the densely settled farmers of central and western Europe? The archaeologist Peter Bellwood has argued that once densely settled farming populations were established in Europe, it would have been practically impossible for other groups coming in to make a demographic dent, as their numbers would, he thought, have been dwarfed by the already established population.³² As an analogy, consider the effect of the British or Mughal occupations of India. Both powers controlled the subcontinent for hundreds of years, but left little trace in the people there today. But ancient DNA shows definitively that major population replacement happened in Europe after around forty-five hundred years ago.

拥有草原血统的人们是如何对一个早已有人定居的地区产生如此巨大影响的呢？一种可能的解释是，在他们之前的农民可能并没有占据中欧所有可利用的经济资源，这给了草原民族扩张的机会。尽管很难根据考古证据估算人口规模，但据估计，两千年前北欧的人口数量大约只有现在的百分之一，甚至更少，这反映了当时耕作方式效率较低、缺乏农药和化肥、没有高产作物品种以及婴儿死亡率较高。 ³³当绳纹器文化传入时，中欧许多耕地都被原始森林环绕。但对丹麦和其他地区花粉记录的研究表明，大约在同一时期，北欧的大片地区从部分森林转变为草原，这表明绳纹器文化的来访者可能砍伐了森林，改造了部分地貌，使其更像草原，并为自己开辟了一片此前该地区居民从未完全占据的生存空间。³⁴

How were people with steppe ancestry able to have such an impact on an already settled region? A possible answer is that the farmers who preceded them may not have occupied every available economic niche in central Europe, giving the steppe peoples an opportunity to expand. Although it is difficult to estimate population sizes from archaeological evidence, the number of people in northern Europe before two thousand years ago has been estimated to be around one hundred times less than today or even smaller, reflecting less efficient farming methods, lack of access to pesticides and fertilizers, the absence of high-yielding plant varieties, and higher infant mortality.³³ When the Corded Ware culture arrived, many tilled fields in central Europe were surrounded by virgin forests. But studies of pollen records in Denmark and elsewhere show that around this time, large parts of northern Europe were transformed from partial forest to grasslands, suggesting that the Corded Ware newcomers may have cut down forests, reengineered parts of the landscape to be more like the steppe, and carved out a niche for themselves that previous peoples of the region had never fully claimed.³⁴

关于草原民族为何能在欧洲定居，还有第二种可能的解释——如果没有古代DNA，这种解释几乎无人会想到。埃斯克·威勒斯列夫和西蒙·拉斯穆森与考古学家克里斯蒂安·克里斯蒂安森合作，提出了一个想法：检测来自欧洲和草原的101个古代DNA样本，寻找病原体的证据。在⁷个样本中，他们发现了鼠疫耶尔森菌的DNA，这种细菌是黑死病的罪魁祸首，据估计，大约700年前，黑死病导致欧洲、印度和中国约三分之一的人口死亡。一个人牙齿上的鼠疫痕迹几乎可以肯定他或她死于鼠疫。他们测序的最早的细菌基因组缺少一些关键基因，这些基因是疾病通过跳蚤传播所必需的，而跳蚤传播是导致腺鼠疫的必要条件。但这些细菌基因组确实携带了导致肺鼠疫所需的基因，肺鼠疫的传播方式与流感类似，都是通过打喷嚏和咳嗽。分析的随机墓穴中有相当一部分携带鼠疫耶尔森菌，这表明这种疾病在草原上是地方性流行病。

There is also a second possible explanation for why the steppe peoples were able to become established in Europe—one that no one would have thought plausible without ancient DNA. Eske Willerslev and Simon Rasmussen, working with the archaeologist Kristian Kristiansen, had the idea of testing 101 ancient DNA samples from Europe and the steppe for evidence of pathogens.³⁵ In seven samples, they found DNA from Yersinia pestis, the bacterium responsible for the Black Death, estimated to have wiped out around one-third of the populations of Europe, India, and China around seven hundred years ago. Traces of plague in a person’s teeth are almost a sure sign that he or she died of it. The earliest bacterial genomes that they sequenced lacked a few key genes necessary for the disease to spread via fleas, which is necessary to cause bubonic plague. But the bacterial genomes did carry the genes necessary to cause pneumonic plague, which is spread by sneezing and coughing just like the flu. That a substantial fraction of random graves analyzed carried Y. pestis shows that this disease was endemic on the steppe.

草原居民是否有可能感染了瘟疫并产生了免疫力，然后将瘟疫传染给了免疫力较弱的中欧农民，导致他们大量死亡？难道是因为欧洲人的衰落而为绳纹器文化的扩张扫清了道路？这岂不是莫大的讽刺？1492年后美洲原住民人口锐减的最重要原因之一，是欧洲人传播的传染病。欧洲人可能因为与家畜近距离接触数千年，对这些疾病产生了一定的免疫力。但美洲原住民大多没有家畜，因此对这些疾病的抵抗力可能要弱得多。那么，五千年前，北欧农民是否也以类似的方式，被来自东方的瘟疫摧毁，从而为草原民族在欧洲的传播铺平了道路呢？

Is it possible that the steppe people had picked up the plague and built up an immunity to it, and then transmitted it to the immunologically susceptible central European farmers, causing their numbers to collapse and thereby clearing the way for the Corded Ware culture expansion? This would be a great irony. One of the most important reasons for the collapse of Native American populations after 1492 was infectious diseases spread by Europeans who plausibly had built up some immunity to these diseases after thousands of years of exposure as a result of living in close proximity to their farm animals. But Native Americans, who by and large lacked domesticated animals, likely had much less resistance to them. Was it possible that, in a similar way, northern European farmers after five thousand years ago were decimated by plagues brought from the east, paving the way for the spread of steppe ancestry through Europe?

英国是如何沦陷的

How Britain Succumbed

在草原民族的浪潮席卷中欧之后，这股浪潮持续推进。大约四千七百年前，在绳纹器文化席卷中欧几个世纪之后，钟形杯文化也出现了同样迅猛的扩张，其起源地可能位于今天的伊比利亚半岛地区。钟形杯文化因其钟形饮用器皿而得名，这些器皿与其他器物（包括装饰纽扣和弓箭手护腕）一起迅速传播到西欧的广大地区。通过研究锶、铅和氧等元素的同位素比例，我们可以了解不同地区物质的特征，从而了解人口和物品的迁徙情况。通过研究牙齿的同位素组成，考古学家发现，钟形杯文化中的一些居民曾迁徙到距离出生地数百公里之外的地方。四千五百年后，钟形杯文化传播到了英国^。

After the wave of steppe ancestry crashed over central Europe, it kept rolling. Beginning around forty-seven hundred years ago, a couple of centuries after the Corded Ware culture swept into central Europe, there was an equally dramatic expansion of the Bell Beaker culture, probably from the region of present-day Iberia. The Bell Beaker culture is named for its bell-shaped drinking vessels that rapidly spread over a vast expanse of western Europe alongside other artifacts including decorative buttons and archers’ wristguards. It is possible to learn about the movement of people and objects by studying the ratios of isotopes of elements like strontium, lead, and oxygen that are characteristic of materials in different parts of the world. By studying the isotopic composition of teeth, archaeologists have shown that some people of the Bell Beaker culture moved hundreds of kilometers from their places of birth.³⁶ Bell Beaker culture spread to Britain after forty-five hundred years ago.

要理解钟形杯文化的传播，一个重要的未解之谜始终是：它的传播究竟是由人口迁徙推动，还是由思想传播推动？二十世纪初，人们认识到钟形杯文化的巨大影响，由此产生了“钟形杯族群”这一浪漫化的概念，认为他们是传播新文化，或许还有凯尔特语的民族。这迎合了当时的民族主义热情。但是，就像对绳纹器文化的宣称一样，这种观点在二战后就不再流行了。

A major open question for understanding the spread of the Bell Beaker culture has always been whether it was propelled by the movement of people or the spread of ideas. At the beginning of the twentieth century, the recognition of the massive impact of the Bell Beaker culture led to the romantic notion of a “Beaker Folk,” a people who disseminated a new culture and perhaps Celtic languages—a nod to the nationalistic fervor of the time. But, like the claim made for the Corded Ware culture, this position fell out of favor after the Second World War.

²⁰¹⁷年，我的实验室成功地从欧洲各地两百多具与钟形杯文化相关的骨骼中收集了全基因组古代DNA数据。博士后研究员伊尼戈·奥拉尔德（Iñigo Olalde）分析了这些数据，结果表明，伊比利亚半岛的个体在基因上与他们之前的非钟形杯文化人群并无区别。但中欧与钟形杯文化相关的个体则截然不同，他们的祖先大多来自草原，与伊比利亚半岛的钟形杯文化相关个体几乎没有共同的祖先。因此，与绳纹器文化从东方传播的情况不同，钟形杯文化最初在欧洲的传播是通过思想的交流而非人口迁徙实现的。

In 2017, my laboratory succeeded in assembling whole-genome ancient DNA data from more than two hundred skeletons associated with the Beaker culture from across Europe.³⁷ Iñigo Olalde, a postdoctoral scientist, analyzed the data to show that individuals in Iberia were genetically indistinguishable from the people who had preceded them and who were not buried in a Bell Beaker culture style. But Bell Beaker–associated individuals in central Europe were extremely different, with most of their ancestry of steppe origin, and little if any ancestry in common with individuals from Iberia associated with the Bell Beaker culture. So, in contrast to what happened with the spread of the Corded Ware culture from the east, the initial spread of the Bell Beaker culture across Europe was mediated by the movement of ideas, not by migration.

然而，当钟形杯文化通过思想传播到达中欧后，它又通过人口迁徙进一步扩散。在钟形杯文化传入英国之前，在我们分析的数十个古代DNA样本中，没有一个样本含有草原血统。但4500年前之后，我们分析的数十个英国古代样本都含有大量的草原血统，并且与伊比利亚人没有任何特殊的亲缘关系。从草原血统的比例来看，从英国数十具钟形杯文化时期骨骼中提取的DNA与英吉利海峡对岸钟形杯文化墓葬中的骨骼DNA高度吻合。这一时期，欧洲大陆人口向不列颠群岛的迁徙对当地基因产生了永久性的影响。在钟形杯文化之后的青铜时代，英国和爱尔兰的³⁸具骨骼最多只有约10%的血统来自这些岛屿上的早期农民，其余90%则来自与荷兰钟形杯文化相关的人群。这次人口更替至少与绳纹器文化传播过程中伴随的人口更替一样剧烈。

Once the Bell Beaker culture reached central Europe through the dispersal of ideas, though, it spread further through migration. Prior to the spread of Beaker culture into Britain, not a single ancient DNA sample from among the many dozen we analyzed had any steppe ancestry. But after forty-five hundred years ago, each one of the many dozens of ancient British samples we analyzed had large amounts of steppe ancestry and no special affinity to Iberians at all. Measured in terms of its proportion of steppe ancestry, DNA extracted from dozens of Bell Beaker skeletons in Britain closely matches that of skeletons from Bell Beaker culture graves across the English Channel. The genetic impact of the spread of peoples from the continent into the British Isles in this period was permanent. British and Irish³⁸ skeletons from the Bronze Age that followed the Beaker period had at most around 10 percent ancestry from the first farmers of these islands, with the other 90 percent from people like those associated with the Bell Beaker culture in the Netherlands. This was a population replacement at least as dramatic as the one that accompanied the spread of the Corded Ware culture.

事实证明，虽然“钟形杯民族”的说法对于英国来说是正确的，但它并不能解释钟形杯文化在整个欧洲大陆的传播。正是古代DNA数据开始为我们提供一个更为细致入微的视角，让我们得以了解史前时期文化的变迁。受古代DNA研究结果的启发，几位考古学家向我推测，钟形杯文化或许可以被视为一种古代宗教，它将不同背景的人们转变为一种新的世界观，从而起到了一种意识形态的融合作用，促进了草原血统和文化在中欧和西欧的融合与传播。在匈牙利的一处钟形杯遗址，我们发现了直接证据，表明这种文化对不同血统的人群持开放态度。在钟形杯文化背景下埋葬的个体，其草原血统的比例从0%到75%不等（与绳纹器文化人群的比例相当）。

It turns out that the discredited idea of the “Beaker Folk” was right for Britain, although wrong as an explanation for the spread of the Bell Beaker culture over the European continent as a whole. So it is that ancient DNA data are beginning to provide us with a more nuanced view of how cultures changed in prehistory. Prompted by the ancient DNA results, several archaeologists have speculated to me that the Bell Beaker culture could be viewed as a kind of ancient religion that converted peoples of different backgrounds to a new way of viewing the world, thus serving as an ideological solvent that facilitated the integration and spread of steppe ancestry and culture into central and western Europe. At a Hungarian Bell Beaker site, we found direct evidence that this culture was open to people of diverse ancestries, with individuals buried in a Bell Beaker cultural context having the full range of steppe ancestry from zero to 75 percent (as high as in people associated with the Corded Ware culture).

是什么使得信奉钟形杯文化的人们能够如此迅速地扩散到西北欧，并最终战胜此前已在那里定居的、高度发达的族群？考古学家认为钟形杯文化与绳纹器文化截然不同，而绳纹器文化又与亚姆纳文化迥然不同。然而，这三种文化都参与了草原血统从东向西的大规模传播，或许尽管它们在文化特征上大相径庭，却也存在着某些共通的意识形态。

What made it possible for people practicing the Beaker culture to spread so dramatically into northwestern Europe and outcompete the established and highly sophisticated populations previously established there? Archaeologists view the Bell Beaker culture as extremely different from the Corded Ware culture, which was in turn extremely different from the Yamnaya culture. Yet all three participated in the massive spread of steppe ancestry from east to west, and perhaps they shared some elements of an ideology despite their very different features.

关于相隔数百公里的不同文化之间存在共同特征的推测，令科学家和考古学家感到不安。但我们应该重视。在基因发现之前，任何关于一种新的世界观可以在考古学上截然不同的文化之间共享的说法，例如亚姆纳文化、绳纹器文化和钟形杯文化，都可能被断然斥为异想天开。但现在我们知道，这些人通过大规模的迁徙联系在一起，其中一些迁徙甚至压倒了早期的文化，这证明这些迁徙产生了深远的影响。我们还需要重新审视语言的传播，这是文化传播的直接体现。如今几乎所有欧洲人都说着密切相关的语言，这证明曾经有一种新的文化在欧洲广泛传播。那么，古代DNA所记录的人口迁徙是否推动了共同语言在欧洲的传播呢？

Speculations about shared features among cultures separated from each other by hundreds of kilometers make scientists and archaeologists uncomfortable. But we should pay attention. Prior to the genetic findings, any claim that a new way of seeing the world could have been shared across cultures as archaeologically different from one another as the Yamnaya, Corded Ware, and Bell Beaker could confidently be dismissed as fanciful. But now we know that these people were linked by major migrations, some of which overwhelmed earlier cultures, providing evidence that these migrations had profound effects. We also need to look again at the spread of language, a direct manifestation of the spread of culture. That almost all Europeans today speak closely related languages is proof that there was strong dissemination of a new culture across Europe at one time. Could the spread of shared languages across Europe have been propelled by the spread of people documented by ancient DNA?

印欧语系的起源

The Origin of Indo-European Languages

史前时代的一大谜团是印欧语系的起源。印欧语系是一组密切相关的语言，如今几乎遍布整个欧洲、亚美尼亚、伊朗和印度北部，但在近东地区却存在着巨大的空白，在过去的五千年里，这些语言只存在于边缘地带——我们之所以知道这一事实，是因为文字是在那里发明的。

A great mystery of prehistory is the origin of Indo-European languages, the closely related group of tongues that today are spoken across almost all of Europe, Armenia, Iran, and northern India, with a great gap in the Near East where these languages only existed at the periphery for the last five thousand years—a fact known to us because writing was invented there.

最早注意到印欧语系语言相似性的人之一是威廉·琼斯，他是一位在加尔各答任职的法官。在英属印度，一位自幼学习希腊语和拉丁语，并研习过梵语——古印度宗教典籍所用的语言——的学者，于1786年写道：“梵语，无论其历史有多么悠久，其结构都堪称奇妙；它比希腊语更完美，比拉丁语更丰富，也比两者都更精妙，然而，无论在动词词根还是语法形式上，它与希腊语和拉丁语都具有比偶然更为强烈的亲缘关系；这种亲缘关系如此之强，以至于任何语言学家在研究这三种语言之后，都会相信它们源自某个共同的源头，而这个源头或许已经不复存在了。” ³⁹两百多年来，学者们一直困惑于如此广袤的地域中，为何会出现如此相似的语言。

One of the first people to note the similarity among Indo-European languages was William Jones, a judge serving in Kolkata in British India, who knew Greek and Latin from his schooldays, and had learned Sanskrit, the language of the ancient Indian religious texts. In 1786, he observed: “The Sanskrit language, whatever may be its antiquity, is of a wonderful structure; more perfect than the Greek, more copious than the Latin, and more exquisitely refined than either, yet bearing to both of them a stronger affinity, both in the roots of verbs and in the forms of grammar, than could possibly have been produced by accident; so strong indeed that no philologer could examine them all three, without believing them to have sprung from some common source, which, perhaps, no longer exists.”³⁹ For more than two hundred years, scholars have puzzled over how such a similarity of languages developed over so vast a region.

1987年，科林·伦弗鲁提出了一个统一的理论来解释印欧语系如何形成如今的分布格局。在他的著作《考古学与语言：印欧语系起源之谜》中，他提出，如今欧亚大陆如此广袤区域语言的同质性可以用同一事件来解释：九千年前，来自安纳托利亚的人们带来了农业，并由此扩散开来。^他的论点基于这样一种理念：农业为安纳托利亚人带来了经济优势，从而使新的人口得以大规模地扩散到欧洲。人类学研究一贯表明，人口的大规模迁徙是小型社会语言演变的必要条件，因此，像印欧语系传播这样影响深远的现象很可能是由大规模人口迁徙推动的。⁴¹由于没有确凿的考古证据表明后来曾发生过大规模的欧洲移民，而且一旦人口密集的农业定居点形成，就很难想象其他族群如何站稳脚跟，因此伦弗鲁及其后的学者得出结论：农业的传播很可能是印欧语系传入欧洲的原因^。42

In 1987, Colin Renfrew proposed a unified theory for how Indo-European languages attained their current distribution. In his book Archaeology and Language: The Puzzle of Indo-European Origins, he suggested that the homogeneity of language across such a vast stretch of Eurasia today could be explained by one and the same event: the spread from Anatolia after nine thousand years ago of peoples bringing agriculture.⁴⁰ His argument was rooted in the idea that farming would have given Anatolians an economic advantage that would have allowed new populations to spread massively into Europe. Anthropological studies have consistently shown that major migrations of people are necessary to achieve language change in small-scale societies, so a phenomenon as profound as the spread of Indo-European languages was likely to have been propelled by mass migration.⁴¹ Since there was no good archaeological evidence for a later major migration into Europe, and since once densely settled farming populations were established it was difficult to imagine how other groups could gain a foothold, Renfrew and scholars who followed him concluded that the spread of farming was probably what brought Indo-European languages to Europe.⁴²

鉴于伦弗鲁当时掌握的数据，他的逻辑颇具说服力，但农业从安纳托利亚传播到欧洲推动印欧语系扩散的论点，已被古代DNA研究的发现所削弱。这些研究表明，大约在五千年前，与绳纹器文化相关的人口大规模迁徙才发生于中欧。文化。伦弗鲁从基本原理出发——即农业传入欧洲之后，人口统计学上不太可能再发生足以引发语言转变的大规模迁徙——构建了一个令人信服的安纳托利亚假说，并赢得了众多支持者。然而，理论终究会被数据推翻，数据显示，亚姆纳人也对人口产生了重大影响——事实上，如今北欧最重要的祖先来源显然是亚姆纳人或与其密切相关的族群。这表明，亚姆纳人的扩张很可能将一个重要的全新语系传播到了整个欧洲。过去几千年来印欧语系在欧洲的普遍存在，以及与亚姆纳人相关的迁徙比农业迁徙发生得更晚，使得欧洲至少部分印欧语系语言，甚至可能全部印欧语系语言，都可能由亚姆纳人传播。 ⁴³

Renfrew’s logic was compelling given the data he had available at the time, but the argument that the spread of farming from Anatolia drove the spread of Indo-European languages into Europe has been undermined by the findings from studies of ancient DNA, which showed that a mass movement of people into central Europe occurred after five thousand years ago in association with the Corded Ware culture. By arguing from first principles—that after the spread of farming into Europe it would not have been demographically plausible for there to have been another migration substantial enough to induce a language shift—Renfrew constructed a compelling case for the Anatolian hypothesis, which won many adherents. But theory is always trumped by data, and the data show that the Yamnaya also made a major demographic impact—in fact, it is clear that the single most important source of ancestry across northern Europe today is the Yamnaya or groups closely related to them. This suggests that the Yamnaya expansion likely spread a major new group of languages throughout Europe. The ubiquity of Indo-European languages in Europe over the last few thousand years, and the fact that the Yamnaya-related migration was more recent than the farming one, makes it likely that at least some Indo-European languages in Europe, and perhaps all of them, were spread by the Yamnaya.⁴³

安纳托利亚假说的主要反驳论点是草原假说——即印欧语系起源于黑海和里海以北的草原。在基因数据出现之前，支持草原假说的最佳论据或许是戴维·安东尼提出的。他指出，当今绝大多数印欧语系语言的共同词汇不太可能与它们起源于大约六千年前相符。他的关键观察是，除了现已灭绝的最古老的安纳托利亚语支（例如古赫梯语）之外，所有现存的印欧语系语言都拥有丰富的关于马车的共同词汇，包括表示车轴、挽具杆和车轮的词语。安东尼将这种词汇共享解释为证据，表明如今从东部的印度到西部的大西洋沿岸，所有印欧语系语言都源自一个使用马车的古代民族所使用的语言。这个族群的生存年代不可能早于大约六千年前，因为考古证据表明，车轮和马车大约在那时开始普及。⁴⁴这个时间排除了安纳托利亚农业在九千年至八千年前向欧洲扩张的可能性。因此，传播当今大多数印欧语系语言的明显候选者是亚姆纳亚人，他们依赖于……马车和车轮的技术大约在五千年前开始普及。

The main counterargument to the Anatolian hypothesis is the steppe hypothesis—the idea that Indo-European languages spread from the steppe north of the Black and Caspian seas. The best single argument for the steppe hypothesis prior to the availability of genetic data may be the one constructed by David Anthony, who has shown that the shared vocabulary of the great majority of present-day Indo-European languages is unlikely to be consistent with their having originated much earlier than about six thousand years ago. His key observation is that all extant branches of the Indo-European language family except for the most anciently diverging Anatolian ones that are now extinct (such as ancient Hittite) have an elaborate shared vocabulary for wagons, including words for axle, harness pole, and wheels. Anthony interpreted this sharing as evidence that all Indo-European languages spoken today, from India in the east to the Atlantic fringe in the west, descend from a language spoken by an ancient population that used wagons. This population could not have lived much earlier than about six thousand years ago, since we know from archaeological evidence that it was around then that wheels and wagons spread.⁴⁴ This date rules out the Anatolian farming expansion into Europe between nine thousand and eight thousand years ago. The obvious candidate for dispersing most of today’s Indo-European languages is thus the Yamnaya, who depended on the technology of wagons and wheels that became widespread around five thousand years ago.

草原牧民大规模迁徙，足以取代定居的农业人口，从而传播一种新的语言，这乍一看似乎在印度比在欧洲更不可思议。阿富汗的高山阻隔了印度与草原之间的联系，而欧洲则没有类似的屏障。然而，草原牧民最终也突破了这道屏障，进入了印度。正如下一章所述，几乎所有印度人都是两个截然不同的祖先群体的混血后裔，其中一个群体约有一半的祖先直接来自亚姆纳亚人。

That there could have been a massive enough migration by steppe pastoralists to displace settled agricultural populations, and thereby distribute a new language, seems on the face of it even more implausible for India than for Europe. India is protected from the steppe by the high mountains of Afghanistan, whereas there is no similar barrier protecting Europe. Yet the steppe pastoralists broke through to India too. As is related in the next chapter, almost everyone in India is a mixture of two highly divergent ancestral populations, one of which derived about half its ancestry directly from the Yamnaya.

虽然基因研究结果表明亚姆纳文化在印欧语系的传播中扮演了核心角色，并最终支持了某种草原起源假说，但这些发现尚未解决印欧语系原始语言的发源地问题，即在亚姆纳文化大规模扩张之前，这些语言的使用地。从赫梯帝国及其邻近古代文明出土的四千年前泥板上发现的安纳托利亚语系语言，并不具备如今所有印欧语系语言都拥有的完整马车和车轮词汇。来自安纳托利亚同时期的古代DNA也未显示出与亚姆纳文化相似的草原祖先特征（尽管此处的证据是间接的，因为目前尚未发表赫梯人自身的古代DNA）。这让我认为，最早使用印欧语系语言的人群最有可能位于高加索山脉以南，或许就在今天的伊朗或亚美尼亚境内，因为从那里发现的古代DNA与亚姆纳亚人和古代安纳托利亚人的祖先人群的DNA特征相符。如果这一推测正确，那么这群人分为两支：一支北迁至草原，与草原上的狩猎采集者以1:1的比例融合，最终形成了前文所述的亚姆纳亚人；另一支则迁徙至安纳托利亚，繁衍出当地使用赫梯语等语言的人群的祖先。

While the genetic findings point to a central role for the Yamnaya in spreading Indo-European languages, tipping the scales definitively in favor of some variant of the steppe hypothesis, those findings do not yet resolve the question of the homeland of the original Indo-European languages, the place where these languages were spoken before the Yamnaya so dramatically expanded. Anatolian languages known from four-thousand-year-old tablets recovered from the Hittite Empire and neighboring ancient cultures did not share the full wagon and wheel vocabulary present in all Indo-European languages spoken today. Ancient DNA available from this time in Anatolia shows no evidence of steppe ancestry similar to that in the Yamnaya (although the evidence here is circumstantial as no ancient DNA from the Hittites themselves has yet been published). This suggests to me that the most likely location of the population that first spoke an Indo-European language was south of the Caucasus Mountains, perhaps in present-day Iran or Armenia, because ancient DNA from people who lived there matches what we would expect for a source population both for the Yamnaya and for ancient Anatolians. If this scenario is right, the population sent one branch up into the steppe—mixing with steppe hunter-gatherers in a one-to-one ratio to become the Yamnaya as described earlier—and another to Anatolia to found the ancestors of people there who spoke languages such as Hittite.

对于局外人来说，DNA 能够对语言之争产生决定性影响，这或许令人惊讶。DNA 当然无法揭示人们曾经使用过的语言。但遗传学能够做到的是……证实人口迁徙确实发生过。如果人们迁徙，就意味着文化交流也随之发生——换句话说，通过基因追踪人口迁徙，也可以追踪文化和语言的潜在传播。通过追踪可能的迁徙路线并排除其他可能性，古代DNA结束了关于印欧语系起源的争论中长达数十年的僵局。安纳托利亚假说失去了其最有力的证据，而草原假说——该假说认为包括古代安纳托利亚语在内的所有印欧语系的最终起源都在草原——也需要修正。DNA已成为遗传学、考古学和语言学新综合研究的核心，这种新研究正在取代过时的理论。

To an outsider, it might seem surprising that DNA can have a definitive impact on a debate about language. DNA cannot of course reveal what languages people spoke. But what genetics can do is to establish that migrations occurred. If people moved, it means that cultural contact occurred too—in other words, genetic tracing of migrations makes it possible also to trace potential spreads of culture and language. By tracing possible migration paths and ruling out others, ancient DNA has ended a decades-old stalemate in the controversy regarding the origins of Indo-European languages. The Anatolian hypothesis has lost its best evidence, and the most common version of the steppe hypothesis—which suggests that the ultimate origin of all Indo-European languages including ancient Anatolian languages was in the steppe—has to be modified too. DNA has emerged as central to the new synthesis of genetics, archaeology, and linguistics that is now replacing outdated theories.

古代DNA革命带来的一个重要启示是，其发现几乎总是对人类迁徙做出与既有模型截然不同的解释，这表明在发明这项新技术之前，我们对人类迁徙和人口形成知之甚少。自19世纪以来，印欧人或“雅利安人”作为“纯种”群体的观点在欧洲引发了民族主义情绪。 ⁴⁵关于凯尔特人、日耳曼人或其他群体是否才是真正的“雅利安人”的争论由来已久，而纳粹种族主义正是在这种争论的推动下滋生的。基因数据似乎为某些观点提供了令人不安的支持——表明一个单一的、基因统一的群体传播了多种印欧语系语言。但数据也揭示了，早期关于血统纯正的讨论是错误的。无论最初的印欧语系使用者生活在近东还是东欧，将印欧语系传播到全球广袤地区的亚姆纳亚人都是由多种族群融合而成的。绳纹器文化的使用者是另一种族群融合的产物，而与钟形杯文化相关的西北欧人则又是另一种族群融合的产物。古DNA研究表明，高度分化的族群之间的大规模迁徙和融合是塑造人类史前史的关键力量，而那些寻求回归神话般纯粹性的意识形态则与严谨的科学相悖。

A great lesson of the ancient DNA revolution is that its findings almost always provide accounts of human migrations that are very different from preexisting models, showing how little we really knew about human migrations and population formation prior to the invention of this new technology. The vision of Indo-Europeans or “Aryans” as a “pure” group has sparked nationalist sentiments in Europe since the nineteenth century.⁴⁵ There were debates about whether the Celts or the Teutons or other groups were the real “Aryans,” and Nazi racism was fueled by this discussion. The genetic data have provided what might seem like uncomfortable support for some of these ideas—suggesting that a single, genetically coherent group was responsible for spreading many Indo-European languages. But the data also reveal that these early discussions were misguided in supposing purity of ancestry. Whether the original Indo-European speakers lived in the Near East or in eastern Europe, the Yamnaya, who were the main group responsible for spreading Indo-European languages across a vast span of the globe, were formed by mixture. The people who practiced the Corded Ware culture were a further mixture, and northwestern Europeans associated with the Bell Beaker culture were yet a further mixture. Ancient DNA has established major migration and mixture between highly divergent populations as a key force shaping human prehistory, and ideologies that seek a return to a mythical purity are flying in the face of hard science.

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形成印度的碰撞

The Collision That Formed India

印度河文明的衰落

The Fall of the Indus Civilization

在印度教最古老的经典《梨俱吠陀》中，战神因陀罗驾着马拉战车，对抗他不洁的敌人（达萨），摧毁他们的堡垒（^普尔），并为他的子民雅利安人（雅利安人）夺取土地和水源。

In the oldest text of Hinduism, the Rig Veda, the warrior god Indra rides against his impure enemies, or dasa, in a horse-drawn chariot, destroys their fortresses, or pur, and secures land and water for his people, the arya, or Aryans.¹

《梨俱吠陀》写于四千年至三千年前，以古梵语写成。在被记录下来之前，它像希腊的《伊利亚特》和《奥德赛》一样，以口头形式流传了约两千年。这两部史诗是在^几百年后用另一种早期印欧语系语言写成的。《梨俱吠陀》为我们了解过去提供了一个非凡的窗口，让我们得以窥见印欧文化在更接近这些语言从共同源头辐射开来的时期可能呈现出的面貌。但是，《梨俱吠陀》中的故事与真实事件有何关联？达萨（dasa）是谁？雅利安（arya）又是谁？堡垒又位于何处？这些故事真的发生过吗？

Composed between four thousand and three thousand years ago in Old Sanskrit, the Rig Veda was passed down orally for some two thousand years before being written down, much like the Iliad and Odyssey in Greece, which were composed several hundred years later in another early Indo-European language.² The Rig Veda is an extraordinary window into the past, as it provides a glimpse of what Indo-European culture might have been like in a period far closer in time to when these languages radiated from a common source. But what did the stories of the Rig Veda have to do with real events? Who were the dasa, who were the arya, and where were the fortresses located? Did anything like this really happen?

20世纪20年代和30年代，人们对​​利用考古学来深入了解这些问题的可能性感到无比兴奋。在那几年里，考古发掘揭示了古代文明的遗迹，包括哈拉帕、摩亨佐达罗以及旁遮普和信德其他地区的城墙环绕的城市，这些城市的历史可以追溯到4500至3800年前。这些城市和较小的城镇在今天的巴基斯坦和印度部分地区，印度河谷星罗棋布着许多村庄，其中一些村庄居住着数万人。3它们会不会就是《梨俱吠陀》中提到的堡垒或“普尔”（pur）^呢？

There was tremendous excitement about the possibility of using archaeology to gain insight into these questions in the 1920s and 1930s. In those years, excavations uncovered the remains of an ancient civilization, walled cities at Harappa, Mohenjo-daro, and elsewhere in the Punjab and Sind that dated from forty-five hundred to thirty-eight hundred years ago. These cities and smaller towns and villages dotted the valley of the river Indus in present-day Pakistan and parts of India, and some of them sheltered tens of thousands of people.³ Were they perhaps the fortresses, or pur, of the Rig Veda?

印度河流域文明的城市四周环绕着城墙，呈网格状布局。它们拥有充足的粮仓，用于储存周边河谷平原耕种所得的粮食。城市里聚集着技艺精湛的工匠，他们擅长加工陶器、黄金、铜器、贝壳和木材。印度河流域文明的人们从事着繁荣的贸易，这体现在他们留下的石制度量衡器皿以及远至阿富汗、阿拉伯、美索不达米亚甚至非洲的贸易伙伴身上。^{他们制作装饰性的印章，上面刻有人物或动物的图案。印章上常常有一些符号或标记，}其含义至今仍未被完全解读。

Indus Valley Civilization cities were surrounded by perimeter walls and laid out on grids. They had ample storage for grain supplied by farming of land in the surrounding river plains. The cities sheltered craftspeople skilled in working clay, gold, copper, shell, and wood. The people of the Indus Valley Civilization engaged in prolific trade and commerce, as reflected in the stone weights and measures they left behind, and their trading partners, who lived as far away as Afghanistan, Arabia, Mesopotamia, and even Africa.⁴ They made decorative seals with images of humans or animals. There were often signs or symbols on the seals whose meaning remains largely undeciphered.⁵

自最初的考古发掘以来，印度河流域文明的许多方面仍然充满谜团，不仅仅是它的文字。最大的谜团在于它的衰落。大约三千八百年前，印度河流域的聚落逐渐减少，人口中心向东迁移至恒河平原。^大约在同一时期，《梨俱吠陀》用古梵语写成。古梵语是当今印度北部绝大多数语言的祖先语言，它在《梨俱吠陀》成书前一千年就与伊朗的语言分化开来。印伊语系又与欧洲几乎所有语言都有亲缘关系，它们共同构成了庞大的印欧语系。 《梨俱吠陀》的宗教，及其掌管自然和规范社会的诸神体系，与印欧语系欧亚大陆其他地区（包括伊朗、希腊和斯堪的纳维亚）的神话有着明显的相似之处，这进一步证明了欧亚大陆广袤区域之间存在着文化联系^。7

Since the original excavations, many things about the Indus Valley Civilization have remained enigmatic, not only its script. The greatest mystery is its decline. Around thirty-eight hundred years ago, the settlements of the Indus dwindled, with population centers shifting east toward the Ganges plain.⁶ Around this time, the Rig Veda was composed in Old Sanskrit, a language that is ancestral to the great majority of languages spoken in northern India today and that had diverged in the millennium before the Rig Veda was composed from the languages spoken in Iran. Indo-Iranian languages are in turn cousins of almost all of the languages spoken in Europe and with them make up the great Indo-European language family. The religion of the Rig Veda, with its pantheon of deities governing nature and regulating society, had unmistakable similarities to the mythology of other parts of Indo-European Eurasia, including Iran, Greece, and Scandinavia, providing further evidence of cultural links across vast expanses of Eurasia.⁷

有人推测，印度河流域文明的衰落是由于来自北方和西方的、讲印欧语系语言的移民（即所谓的印度-雅利安人）的到来所致。在《梨俱吠陀》中，入侵者拥有马匹和战车。然而，考古学表明，印度河流域文明是一个马匹出现之前的社会。在其遗址中，既没有马匹存在的明确证据，也没有辐条轮车辆的遗迹，尽管……陶土制成的牛拉车模型。8^马匹和辐条轮战车是青铜时代欧亚大陆的大规模杀伤性武器。印度-雅利安人是否利用他们的军事技术终结了古老的印度河流域文明？

Some have speculated that the collapse of the Indus Valley Civilization was caused by the arrival in the region of migrants from the north and west speaking Indo-European languages, the so-called Indo-Aryans. In the Rig Veda, the invaders had horses and chariots. We know from archaeology that the Indus Valley Civilization was a pre-horse society. There is no clear evidence of horses at their sites, nor are there remains of spoke-wheeled vehicles, although there are clay figurines of wheeled carts pulled by cattle.⁸ Horses and spoke-wheeled chariots were the weapons of mass destruction of Bronze Age Eurasia. Did the Indo-Aryans use their military technology to put an end to the old Indus Valley Civilization?

自哈拉帕遗址发掘以来，“雅利安人入侵理论”便被欧洲和印度的民族主义者所利用，这使得客观地讨论这一理论变得困难。包括纳粹在内的欧洲种族主义者被这样一种观念所吸引：印度曾遭受入侵，肤色较深的居民被与北欧人有亲缘关系的肤色较浅的战士征服，后者强加给他们一套等级森严的种姓制度，禁止不同群体之间的通婚。在纳粹和其他一些人看来，印欧语系的分布——将欧洲与印度联系起来，却对近东及其犹太人影响甚微——象征着一场古老的征服：征服者从祖先的故土出发，驱逐并奴役被征服地区的人民，而他们也渴望效仿这一历史事件。9一些人^甚至将印度-雅利安人的祖先故土定位在东北欧，包括德国。他们还将吠陀神话中的一些元素融入自身文化，自称为雅利安人，这个名称源自《梨俱吠陀》，并挪用了卍字——印度教中象征吉祥的传统符号^。10

Since the original excavations at Harappa, the “Aryan invasion theory” has been seized on by nationalists in both Europe and India, which makes the idea difficult to discuss in an objective way. European racists, including the Nazis, were drawn to the idea of an invasion of India in which the dark-skinned inhabitants were subdued by light-skinned warriors related to northern Europeans, who imposed on them a hierarchical caste system that forbade intermarriage across groups. To the Nazis and others, the distribution of the Indo-European language family, linking Europe to India and having little impact on the Near East with its Jews, spoke of an ancient conquest moving out of an ancestral homeland, displacing and subjugating the peoples of the conquered territories, an event that they wished to emulate.⁹ Some placed the ancestral homeland of the Indo-Aryans in northeast Europe, including Germany. They also adopted features of Vedic mythology as their own, calling themselves Aryans after the term in the Rig Veda, and appropriating the swastika, a traditional Hindu symbol of good fortune.¹⁰

纳粹对移民和印欧语系传播的兴趣，使得欧洲严肃的学者难以探讨移民传播印欧语系的可能性。 ¹¹在印度，印度河谷文明是否因来自北方的印欧语系移民而衰落，也存在争议，因为它暗示南亚文化的重要元素可能受到了外来影响。

The Nazis’ interest in migrations and the spread of Indo-European languages has made it difficult for serious scholars in Europe to discuss the possibility of migrations spreading Indo-European languages.¹¹ In India, the possibility that the Indus Valley Civilization fell at the hands of migrating Indo-European speakers coming from the north is also fraught, as it suggests that important elements of South Asian culture might have been influenced from the outside.

学者们不再认同北方大规模迁徙的观点，不仅因为这一观点已被过度政治化，还因为考古学家们意识到，考古记录中出现的重大文化变迁并不总是意味着大规模的人口迁徙。事实上，几乎没有考古证据表明存在这样的人口迁徙。大约三千八百年前，并没有明显的灰烬层和破坏痕迹表明印度河流域城镇曾遭到焚毁和洗劫。相反，有证据表明，印度河流域文明的衰落是一个漫长的过程。数十年来，城镇人口外流和环境恶化加剧了这一现象。但缺乏考古证据并不意味着没有发生过大规模的外来入侵。大约在1600至1500年前，西罗马帝国在日耳曼扩张的压力下崩溃，西哥特人和汪达尔人先后洗劫罗马并控制罗马行省，给西罗马帝国造成了巨大的政治和经济打击。然而，迄今为止，似乎很少有考古证据表明这一时期罗马城市遭到破坏，如果没有详细的历史记载，我们可能根本不知道这些关键事件的发生。 ¹² 印度河流域人口明显减少的情况也可能与我们难以发现突发变化有关。考古发现所呈现的模式可能掩盖了更为突发的触发事件。

The idea of a mass migration from the north has fallen out of favor among scholars not only because it has become so politicized, but also because archaeologists have realized that major cultural shifts in the archaeological record do not always imply major migrations. And, in fact, there is scant archaeological evidence for such a population movement. There are no obvious layers of ash and destruction around thirty-eight hundred years ago suggesting the burning and sacking of the Indus towns. If anything, there is evidence that the Indus Valley Civilization’s decline played out over a long period, with emigration away from the towns and environmental degradation taking place over decades. But the lack of archaeological evidence does not mean that there were no major incursions from the outside. Between sixteen hundred and fifteen hundred years ago, the western Roman Empire collapsed under the pressure of the German expansions, with great political and economic blows dealt to the western Roman Empire when the Visigoths and the Vandals each sacked Rome and took political control of Roman provinces. However, there so far seems to be little archaeological evidence for destruction of Roman cities in this time, and if not for the detailed historical accounts, we might not know these pivotal events occurred.¹² It is possible that in the apparent depopulation of the Indus Valley, too, we might be limited by the difficulty archaeologists have in detecting sudden change. The patterns evident from archaeology may be obscuring more sudden triggering events.

遗传学能提供什么信息？它无法告诉我们印度河流域文明末期究竟发生了什么，但它可以告诉我们，当时是否存在祖先背景迥异的人群之间的碰撞。虽然基因混合本身并不能证明迁徙，但基因混合的证据表明，在哈拉帕文明衰落前后，人口结构发生了剧烈的变化，从而带来了文化交流的机会。

What can genetics add? It cannot tell us what happened at the end of the Indus Valley Civilization, but it can tell us if there was a collision of peoples with very different ancestries. Although mixture is not by itself proof of migration, the genetic evidence of mixture proves that dramatic demographic change and thus opportunity for cultural exchange occurred close to the time of the fall of Harappa.

碰撞之地

A Land of Collisions

大约一千万年前，印度板块向北穿过印度洋与欧亚板块碰撞，形成了雄伟的喜马拉雅山脉。如今的印度也是不同文化和民族碰撞的产物。

The great Himalayas were formed around ten million years ago by the collision of the Indian continental plate, moving northward through the Indian Ocean, with Eurasia. India today is also the product of collisions of cultures and people.

以农业为例。印度次大陆是世界粮仓之一——如今养活了世界四分之一的人口——自五万年前现代人类在欧亚大陆扩张以来，它一直是人口中心之一。然而，农业并非起源于印度。如今的印度农业是欧亚大陆两大农业体系碰撞的产物。近东冬季降雨作物，如小麦和大麦，逐渐被引入印度。根据考古证据，印度河流域的作物大约在九千年前出现，例如，在位于今巴基斯坦境内印度河流域西缘的古代梅赫尔加尔遗址就发现了相关证据。 ¹³大约五千年前，当地农民成功培育出适应季风夏季降雨模式的作物，这些作物随后传播到印度半岛。 ¹⁴大约五千年前，中国的水稻和小米等季风夏季降雨作物也传入了印度半岛。印度可能是近东和中国作物种植体系首次碰撞的地方。

Consider farming. The Indian subcontinent is one of the breadbaskets of the world—today it feeds a quarter of the world’s population—and it has been one of the great population centers ever since modern humans expanded across Eurasia after fifty thousand years ago. Yet farming was not invented in India. Indian farming today is born of the collision of the two great agricultural systems of Eurasia. The Near Eastern winter rainfall crops, wheat and barley, reached the Indus Valley sometime after nine thousand years ago according to archaeological evidence—as attested, for example, in ancient Mehrgarh on the western edge of the Indus Valley in present-day Pakistan.¹³ Around five thousand years ago, local farmers succeeded in breeding these crops to adapt to monsoon summer rainfall patterns, and the crops spread into peninsular India.¹⁴ The Chinese monsoon summer rainfall crops of rice and millet also reached peninsular India around five thousand years ago. India may have been the first place where the Near Eastern and the Chinese crop systems collided.

语言是另一种融合。印度北部的印欧语系语言与伊朗和欧洲的语言相关。主要由印度南部人使用的达罗毗荼语系语言与南亚以外的语言关系不密切。此外，居住在印度北部山区的一些族群使用汉藏语系语言，而东部和中部的一些部落群体则使用南亚语系语言，这些语言与柬埔寨语和越南语相关，据信源自最早将水稻种植带到南亚和东南亚部分地区的民族所使用的语言。《梨俱吠陀》中出现了源自古代达罗毗荼语系和南亚语系语言的词汇，语言学家可以识别出这些词汇并非典型的印欧语系语言，这表明这些语言在印度至少已有三四千年的接触历史。 ¹⁵

Language is another blend. The Indo-European languages of the north of India are related to the languages of Iran and Europe. The Dravidian languages, spoken mostly by southern Indians, are not closely related to languages outside South Asia. There are also Sino-Tibetan languages spoken by groups living in the mountains fringing the north of India, and small pockets of tribal groups in the east and center that speak Austroasiatic languages related to Cambodian and Vietnamese, and that are thought to descend from the languages spoken by the peoples who first brought rice farming to South Asia and parts of Southeast Asia. Words borrowed from ancient Dravidian and Austroasiatic languages, which linguists can detect as they are not typical of Indo-European languages, are present in the Rig Veda, implying that these languages have been in contact in India for at least three or four thousand years.¹⁵

印度人的外貌也多种多样，这直观地证明了种族融合的存在。漫步在印度任何一座城市的街道上，都能清晰地感受到印度人的多样性。肤色从深到浅，不一而足。有些人的面部特征酷似欧洲人，有些人则更接近中国人。人们很容易认为，这些差异反映了过去不同族群的融合，而如今不同族群的融合比例也各不相同。但我们也不能过度解读外貌特征，因为众所周知，外貌也会受到环境和饮食的影响。

The people of India are also diverse in appearance, providing visual testimony to mixture. A stroll down a street in any Indian city makes it clear how diverse Indians are. Skin shades range from dark to pale. Some people have facial features like Europeans, others closer to Chinese. It is tempting to think that these differences reflect a collision of peoples who mixed at some point in the past, with different proportions of mixture in different groups living today. But it is also possible to overinterpret physical appearances, as it is known that appearances can also reflect environment and diet.

印度最早的基因研究得出了看似矛盾的结果。研究人员研究了线粒体DNA（总是由母亲遗传），发现印度人体内绝大多数线粒体DNA是次大陆特有的，他们估计……研究表明，印度线粒体DNA类型仅与数万年前南亚以外地区占主导地位的线粒体DNA类型具有共同祖先。 ¹⁶这表明，在母系方面，印度祖先长期以来大多与次大陆隔绝，未与西部、东部或北部的邻近人群发生基因混合。相比之下，印度相当一部分父系遗传的Y染色体与西欧亚人（欧洲人、中亚人和近东人）的亲缘关系更近，这表明存在基因混合。 ¹⁷

The first genetic work in India gave seemingly contradictory results. Researchers studying mitochondrial DNA, always passed down from mothers, found that the vast majority of mitochondrial DNA in Indians was unique to the subcontinent, and they estimated that the Indian mitochondrial DNA types only shared common ancestry with ones predominant outside South Asia many tens of thousands of years ago.¹⁶ This suggested that on the maternal line, Indian ancestors had been largely isolated within the subcontinent for a long time, without mixing with neighboring populations to the west, east, or north. In contrast, a good fraction of Y chromosomes in India, passed from father to son, showed closer relatedness to West Eurasians—Europeans, central Asians, and Near Easterners—suggesting mixture.¹⁷

由于这些看似矛盾的研究结果，一些印度历史学家已经束手无策，对基因信息不屑一顾。雪上加霜的是，基因学家并没有接受过考古学、人类学和语言学方面的正规训练——而这些领域一直是人类史前研究的主导学科——他们在总结这些领域的研究成果时，很容易犯一些低级错误，或者被一些已知的谬误所误导。但是，忽视基因学是愚蠢的。我们基因学家或许是人类历史研究领域姗姗来迟的“蛮族”，但忽视“蛮族”永远都不是明智之举。我们掌握着前所未有的数据，并且正在利用这些数据来解答那些此前难以触及的关于古代民族构成的问题。

Some historians of India have thrown up their hands and discounted genetic information due to these apparently conflicting findings. The situation has not been helped by the fact that geneticists do not have formal training in archaeology, anthropology, and linguistics—the fields that have dominated the study of human prehistory—and are prone to make elementary mistakes or to be tripped up by known fallacies when summarizing findings from those fields. But it is foolhardy to ignore genetics. We geneticists may be the barbarians coming late to the study of the human past, but it is always a bad idea to ignore barbarians. We have access to a type of data that no one has had before, and we are wielding these data to address previously unapproachable questions about who ancient peoples were.

安达曼小岛上的与世隔绝的人们

The Isolated People of Little Andaman Island

我对印度史前史的研究始于 2007 年，当时我写了一本书和一封信。

My research into the prehistory of India began in 2007 with a book and a letter.

这本书是卢卡·卡瓦利-斯福尔扎的巨著《人类基因的历史与地理》，书中提到了孟加拉湾安达曼群岛的“尼格利陀人”，他们距离大陆数百公里。在现代人类向欧亚大陆迁徙的大部分历史时期，安达曼群岛一直被深海屏障隔绝，尽管其中最大的岛屿——大安达曼岛——在过去几百年里受到了大陆的巨大影响（英国曾将其用作殖民监狱）。北森蒂纳尔岛上居住着世界上最后一个基本未与外界接触的民族之一。世界上的石器时代居民——一个由数百人组成的群体，如今受到印度政府的保护，免受外界干涉。他们如此与众不同，以至于在2004年印度洋海啸后，他们曾向前来救援的印度直升机射箭。安达曼人说的语言与欧亚大陆上任何其他语言都截然不同，以至于无法追溯到任何语言之间的联系。他们的外貌也与附近居住的其他人种大相径庭，体型更瘦小，头发卷曲紧密。卡瓦利-斯福尔扎在他的书中推测，安达曼人可能是现代人类最早走出非洲的后裔，他们或许是在大约五万年前那次大规模迁徙之前就已迁徙至此，而那次迁徙造就了当今大多数非非洲人的祖先。

The book was The History and Geography of Human Genes, Luca Cavalli-Sforza’s magnum opus, in which he mentions the “Negrito” people of the Andaman Islands in the Bay of Bengal, hundreds of kilometers from the mainland. The Andaman Islands have remained isolated by deep sea barriers for most of the history of modern human dispersal through Eurasia, although the largest, Great Andaman, has been massively disrupted by mainland influence over the last few hundred years (the British used it as a colonial prison). North Sentinel Island is populated by one of the last largely uncontacted Stone Age peoples of the world—a group of several hundred people who are now protected from outside interference by the Indian government, and who are so not-of-our-world that they shot arrows at Indian helicopters sent to offer help after the Indian Ocean tsunami of 2004. The Andamanese speak languages that are so different from any others in Eurasia that they have no traceable connections. They also look very different from other humans living nearby, with slighter frames and tightly coiled hair. In one section of his book, Cavalli-Sforza speculated that the Andamanese might represent isolated descendants of the earliest expansions of modern humans out of Africa, perhaps having moved there before the migration that occurred after around fifty thousand years ago and that gave rise to most of the ancestry of non-Africans today.

读到这篇文章后，我和同事们给印度海得拉巴细胞与分子生物学中心（CCMB）的拉尔吉·辛格（Lalji Singh）和库马拉萨米·坦加拉杰（Kumarasamy Thangaraj）写了一封信。几年前，辛格和坦加拉杰曾发表过一篇关于安达曼群岛居民线粒体和Y染色体DNA的论文。^他们的研究表明，小安达曼岛的居民与欧亚大陆的居民已经分离了数万年。我询问他们是否有可能分析安达曼人的全基因组，以获得更全面的了解。

On reading this, my colleagues and I wrote a letter to Lalji Singh and Kumarasamy Thangaraj of the Centre for Cellular and Molecular Biology (CCMB) in Hyderabad, India. A few years earlier, Singh and Thangaraj had published a paper on mitochondrial and Y-chromosome DNA from people of the Andaman Islands.¹⁸ Their study showed that the people of Little Andaman Island had been separated for tens of thousands of years from peoples of the Eurasian mainland. I asked them whether it would be possible to analyze whole genomes of the Andamanese, to gain a fuller picture.

辛格和坦加拉杰非常乐意合作，并很快说服我，这项研究还涉及印度大陆居民，意义更为广泛。他们为我们提供了庞大的DNA样本库。在CCMB的冷冻库中，他们收集了代表印度非凡人类多样性的样本——据我上次查看，该样本库包含三百多个群体和一万八千多个个体DNA样本。这些样本由来自印度各地的学生收集，他们走访村庄，采集祖父母来自同一地区和群体的人们的血液样本。我们从CCMB的样本库中挑选了二十五个群体，这些群体在地理、文化和语言方面尽可能地具有多样性。这些群体涵盖了印度种姓制度中传统的高低社会地位群体，也包括一些完全不属于种姓制度的部落。

Singh and Thangaraj were excited to collaborate and quickly convinced me that there was a broader picture to paint involving mainland Indians as well. They offered us access to a vast collection of DNA. In the freezers at CCMB, they had assembled samples that represented the extraordinary human diversity of India—the last time I checked, the collection included more than three hundred groups and more than eighteen thousand individual DNA samples. These had been assembled by students from all over India who had visited villages and collected blood samples from people whose grandparents were from the same location and group. From the CCMB collection, we selected twenty-five groups that were as diverse as possible geographically, culturally, and linguistically. The groups were of traditionally high as well as low social status in the Indian caste system, and also included a number of tribes entirely outside the caste system.

几个月后，Thangaraj来到了我们在波士顿的实验室。他带来了这套独特而珍贵的DNA样本。我们使用单核苷酸多态性（SNP）微阵列技术对其进行了分析。这项技术当时在美国刚刚问世，但在印度尚未普及。因此，坦加拉杰获得了印度政府的许可，可以将这些DNA样本带出印度。（印度有相关法规限制生物材料的出口，前提是相关研究可以在国内完成。）

A few months later, Thangaraj came to our laboratory in Boston, bringing with him this unique and precious set of DNA samples. We analyzed them using a single nucleotide polymorphism (SNP) microarray, a technology that had just recently become available in the United States but was not yet available in India. For this reason, Thangaraj had been granted permission by the Indian government to take the DNA outside India. (There are Indian regulations limiting export of biological material if the research can be achieved within the country.)

SNP微阵列包含数十万个微小像素，每个像素都覆盖着人工合成的DNA片段，这些片段来自科学家选定的基因组分析位点。当DNA样本流过微阵列时，与人工合成DNA序列重叠的片段会紧密结合，而未重叠的片段则会被洗掉。基于与这些“诱饵”序列结合的相对强度，检测荧光的相机可以确定一个人基因组中可能携带的基因类型。我们分析的SNP微阵列……Lyzed技术能够研究基因组中数十万个位点，这些位点携带某些人特有的突变，而另一些人则没有。通过研究这些位点，可以确定哪些人与哪些人亲缘关系最近。由于该技术专注于特定位点——那些在人群中往往存在差异的位点，因此能够提供关于群体历史的最丰富信息，所以其成本远低于对整个人类基因组进行测序。

A SNP microarray contains hundreds of thousands of microscopic pixels, each of which is covered by artificially synthesized stretches of DNA from the places in the genome that scientists have chosen to analyze. When a DNA sample is washed over the microarray, the fragments that overlap the artificial DNA sequences bind tightly, and the fragments that do not are washed away. Based on the relative intensity of binding to these bait sequences, a camera that detects fluorescent light can determine which possible genetic types a person carries in his or her genome. The SNP microarray that we analyzed was able to study many hundreds of thousands of positions in the genome that harbor a mutation carried by some people but not others. By studying these positions, it is possible to determine which people are most closely related to which others. The technique is much less expensive than sequencing a whole human genome since it zeroes in on points of interest—those that tend to differ among people and thus provide the greatest density of information about population history.

为了初步了解样本之间的关联，我们采用了主成分分析这一数学方法。该方法在前一章关于西欧亚人口历史的描述中也有提及，它能够找到DNA中单碱基变化组合，从而最有效地反映不同人群之间的差异。我们运用这种方法将印度人的遗传数据绘制在二维图上，发现样本沿着一条线分布。这条线的末端是西欧亚人群——包括欧洲人、中亚人和近东人——为了便于比较，我们将其纳入了分析。我们将这条线上非西欧亚人群的部分称为“印度人梯度”：它是印度人群变异的梯度，在图上像箭头一样直接指向西欧亚人群。 ¹⁹

To obtain an initial picture of how the samples were related to each other, we used the mathematical technique of principal component analysis, which is also described in the previous chapter on West Eurasian population history, and which finds combinations of single-letter changes in DNA that are most informative about the differences among people. Using this method to display Indian genetic data on a two-dimensional graph, we found that the samples spread out along a line. At the far extreme of the line were West Eurasian individuals—Europeans, central Asians, and Near Easterners—which we had included in the analysis for the sake of comparison. We called the non–West Eurasian part of the line the “Indian Cline”: a gradient of variation among Indian groups that pointed on the plot like an arrow directly at West Eurasians.¹⁹

主成分分析图中的梯度可能由几种截然不同的历史因素造成，但这种显著的模式使我们推测，当今许多印度族群可能是不同比例的西欧亚相关祖先群体和另一个截然不同的群体的混合体。鉴于印度最南端的族群（也讲达罗毗荼语系）在图中往往与西欧亚人群距离最远，我们探索了一个模型，该模型认为当今的印度人是由两个祖先群体混合而成，并评估了该模型与数据的一致性。

A gradient in a principal component analysis plot can be caused by several quite different histories, but such a striking pattern led us to guess that many Indian groups today might be mixtures, in different proportions, of a West Eurasian–related ancestral population and another very different population. Seeing that the southernmost groups in India—which also spoke Dravidian languages—tended to be farthest away from West Eurasians in the plot, we explored a model in which Indians today are formed from a mixture of two ancestral populations, and we evaluated the consistency of this model with the data.

^{为了检验是否发生了基因混合，我们必须开发新的方法。我们在2010年用来证明尼安德特人和现代人}之间发生过基因混合的方法，实际上最初是为研究印度人口历史而开发的。

To test whether mixture occurred, we had to develop new methods. The methods that we applied in 2010 to show that mixture had occurred between Neanderthals and modern humans²⁰ were in fact primarily developed to study Indian population history.

我们首先检验了欧洲人和印度人是否起源于一个共同的祖先群体，该群体在更早的时候就已分化的假设。我们研究了汉族等东亚人的祖先。我们识别出欧洲人和印度人基因组中存在差异的DNA碱基对，然后测量了中国样本中欧洲人和印度人基因型出现的频率。我们发现，中国人与印度人共享的DNA碱基对明显多于与欧洲人共享的。这排除了欧洲人和印度人自与中国人祖先分离以来，都起源于同一同质祖先群体的可能性。

We first tested the hypothesis that Europeans and Indians descend from a common ancestral population that split at an earlier time from the ancestors of East Asians such as Han Chinese. We identified DNA letters where European and Indian genomes differed, and then measured how often Chinese samples had the genetic types seen in Europeans or Indians. We found that Chinese clearly share more DNA letters with Indians than they do with Europeans. That ruled out the possibility that Europeans and Indians descended from a common homogeneous ancestral population since their separation from the ancestors of Chinese.

我们随后检验了另一种假设，即中国人和印度人自与欧洲人祖先分离后，都起源于同一个祖先群体。然而，这一假设也站不住脚：欧洲人群与所有印度人的亲缘关系比与所有中国人的亲缘关系更近。

We then tested the alternative hypothesis that Chinese and Indians descend from a common ancestral population since their separation from the ancestors of Europeans. However, this scenario did not hold up either: European groups are more closely related to all Indians than to all Chinese.

我们发现，所有印度人所表现出的基因突变频率平均而言介于欧洲人和东亚人之间。这种模式的出现只能是古代人群混合的结果——其中一部分与欧洲人、中亚人和近东人有亲缘关系，另一部分则与东亚人有较远的亲缘关系。

We found that the frequencies of the genetic mutations seen in all Indians are, on average, intermediate between those in Europeans and East Asians. The only way that this pattern could arise was through mixture of ancient populations—one related to Europeans, central Asians, and Near Easterners, and another related distantly to East Asians.

我们最初将第一个人群称为“西欧亚人”，以此来指代欧洲、近东和中亚的大量人群，这些人群之间基因突变频率的差异很小。这些差异通常比欧洲人和东亚人之间的差异小十倍左右。令人惊讶的是，我们发现构成当今印度人祖先的两个人群中，有一个与西欧亚人聚类在一起。在我们看来，这似乎是古代西欧亚人祖先分布的最东端，在那里它与其他截然不同的人群混合在一起。我们可以看到，另一个人群与当今的东亚人（例如中国人）关系更密切，但显然也与他们相隔数万年。因此，它代表了一个早期分化的谱系，对当今南亚人的祖先有所贡献，但对其他地区的人群贡献甚微。

We initially called the first population “West Eurasians,” as a way of referring to the large set of populations in Europe, the Near East, and central Asia, among which there are only modest differences in the frequencies of genetic mutations from one group to another. These differences are typically about ten times smaller than the differences between Europeans and the people of East Asia. It was striking to find that one of the two populations contributing to the ancestry of Indians today grouped with West Eurasians. This looked to us like the easternmost edge of the ancient distribution of West Eurasian ancestry, where it had mixed with other very different people. We could see that the other population was more closely related to present-day East Asians such as Chinese, but was also clearly tens of thousands of years separated from them. So it represented an early-diverging lineage that contributed to people living today in South Asia but not much to people living anywhere else.

在确定了这种混血之后，我们开始寻找可能未受其影响的现代印度人群。所有生活在印度大陆的人群都具有一些西欧亚相关的血统。然而，小安达曼岛的居民没有发现任何异常。安达曼人被认为是古代东亚相关人群的后裔，而该人群对南亚人种的形成做出了贡献。尽管小安达曼岛的土著居民人数不足百人，但他们对于理解印度的人口历史却至关重要。

Having identified the mixture, we searched for present-day Indian populations that might have escaped it. All the populations on the mainland had some West Eurasian–related ancestry. However, the people of Little Andaman Island had none. The Andamanese were consistent with being isolated descendants of an ancient East Asian–related population that contributed to South Asians. The indigenous people of Little Andaman Island, despite a census size of fewer than one hundred, turned out to be key to understanding the population history of India.

东西方文化的融合

The Mixing of East and West

我科学生涯中最紧张的 24 小时发生在 2008 年 10 月，当时我和我的合作者 Nick Patterson 前往海得拉巴与 Singh 和 Thangaraj 讨论这些初步结果。

The tensest twenty-four hours of my scientific career came in October 2008, when my collaborator Nick Patterson and I traveled to Hyderabad to discuss these initial results with Singh and Thangaraj.

10月28日的会面充满挑战。辛格和坦加拉杰似乎要否决整个项目。会前，我们向他们展示了研究结果的概要，即当今印度人是由两个高度分化的祖先群体混合而成，其中一个是“西欧亚人”。辛格和坦加拉杰反对这种说法，他们认为这暗示西欧亚人曾大规模迁徙到印度。他们正确地指出，我们的数据并没有提供直接证据支持这一结论。他们甚至推测，也可能存在反向迁徙，即印度人迁徙到近东和欧洲。根据他们自己的线粒体DNA研究，他们清楚地认识到，如今印度绝大多数线粒体DNA谱系已经在次大陆生活了数万年。²¹他们不愿参与一项暗示西欧亚大陆大规模入侵印度的研究，因为他们无法完全确定如何将全基因组数据与线粒体DNA的研究结果相协调。他们还暗示，提出西欧亚大陆移民的说法在政治上会引发轩然大波。他们虽然没有明确指出这一点，但其言外之意显然是认为来自印度以外的移民对次大陆产生了变革性的影响。

Our meeting on October 28 was challenging. Singh and Thangaraj seemed to be threatening to nix the whole project. Prior to the meeting, we had shown them a summary of our findings, which were that Indians today descend from a mixture of two highly divergent ancestral populations, one being “West Eurasians.” Singh and Thangaraj objected to this formulation because, they argued, it implied that West Eurasian people migrated en masse into India. They correctly pointed out that our data provided no direct evidence for this conclusion. They even reasoned that there could have been a migration in the other direction, of Indians to the Near East and Europe. Based on their own mitochondrial DNA studies, it was clear to them that the great majority of mitochondrial DNA lineages present in India today had resided in the subcontinent for many tens of thousands of years.²¹ They did not want to be part of a study that suggested a major West Eurasian incursion into India without being absolutely certain as to how the whole-genome data could be reconciled with their mitochondrial DNA findings. They also implied that the suggestion of a migration from West Eurasia would be politically explosive. They did not explicitly say this, but it had obvious overtones of the idea that migration from outside India had a transformative effect on the subcontinent.

辛格和坦加拉杰提出了“基因共享”一词来描述西欧亚人和印度人之间的关系。这可能暗示着我们拥有共同的祖先血统。然而，我们的基因研究表明，两个不同人群之间确实发生过一次深刻的融合，并且这种融合对几乎所有现代印度人的祖先都有所贡献；而他们的说法却并未排除融合从未发生的可能性。我们陷入了僵局。当时我觉得，出于政治考量，我们无法公开我们的发现。

Singh and Thangaraj suggested the term “genetic sharing” to describe the relationship between West Eurasians and Indians, a formulation that could imply common descent from an ancestral population. However, we knew from our genetic studies that a real and profound mixture between two different populations had occurred and made a contribution to the ancestry of almost every Indian living today, while their suggestion left open the possibility that no mixture had happened. We came to a standstill. At the time I felt that we were being prevented by political considerations from revealing what we had found.

那天晚上，正值印度教最重要的节日之一——排灯节，烟花噼啪作响，一群小男孩在我们院子外的卡车车轮下扔着仙女棒。我和帕特森躲在他位于辛格和坦加拉杰科学研究所的客房里，试图弄明白这一切究竟是怎么回事。我们逐渐意识到，我们的发现背后蕴含着怎样的文化意义。于是，我们开始摸索，试图找到一种既科学严谨又能兼顾这些问题的解释。

That evening, as the fireworks of Diwali, one of the most important holidays of the Hindu year, crackled, and as young boys threw sparklers beneath the wheels of moving trucks outside our compound, Patterson and I holed up in his guest room at Singh and Thangaraj’s scientific institute and tried to understand what was going on. The cultural resonances of our findings gradually became clear to us. So we groped toward a formulation that would be scientifically accurate as well as sensitive to these issues.

第二天，全体成员在辛格的办公室再次集合。我们坐在一起，为古代印度人群提出了新的名称。我们写道，如今的印度人是两个高度分化的人群——“北印度祖先”（ANI）和“南印度祖先”（ASI）——混合的结果。在混合之前，这两个人群之间的差异就像今天的欧洲人和东亚人一样。北印度祖先与欧洲人、中亚人、近东人和高加索人有亲缘关系，但我们并未提及他们的故乡位置或任何迁徙路线。南印度祖先则与印度以外的任何现代人群都没有亲缘关系。我们证明，北印度祖先和南印度祖先在印度境内发生了剧烈的混合。结果是，如今印度大陆的每个人都是西欧亚人祖先和东亚及南亚不同人群祖先的混合体，尽管比例各不相同。印度没有任何一个人群可以声称自己拥有纯正的基因。

The next day, the full group reconvened in Singh’s office. We sat together and came up with new names for ancient Indian groups. We wrote that the people of India today are the outcome of mixtures between two highly differentiated populations, “Ancestral North Indians” (ANI) and “Ancestral South Indians” (ASI), who before their mixture were as different from each other as Europeans and East Asians are today. The ANI are related to Europeans, central Asians, Near Easterners, and people of the Caucasus, but we made no claim about the location of their homeland or any migrations. The ASI descend from a population not related to any present-day populations outside India. We showed that the ANI and ASI had mixed dramatically in India. The result is that everyone in mainland India today is a mix, albeit in different proportions, of ancestry related to West Eurasians, and ancestry more closely related to diverse East Asian and South Asian populations. No group in India can claim genetic purity.

血统、权力和性支配

Ancestry, Power, and Sexual Dominance

得出这一结论后，我们能够估算出每个印度人群中与西欧亚相关的血统比例。

Having come to this conclusion, we were able to estimate the fraction of West Eurasian–related ancestry in each Indian group.

为了进行这些估算，我们分别测量了西欧亚人基因组与印度人基因组以及小安达曼岛居民基因组的匹配程度。小安达曼岛居民在此至关重要，因为他们与南亚人（ASI）有亲缘关系（尽管较远），但并不像所有印度大陆居民那样具有西欧亚相关的祖先成分，因此我们可以将他们作为分析的参考点。然后，我们重复了上述分析，这次用高加索地区居民的基因组替换了印度人基因组，以测量如果一个基因组完全具有西欧亚相关的祖先成分，我们预期的匹配率应该是多少。通过比较这两个数值，我们可以提出这样的问题：“每个印度人群与我们预期中完全具有西欧亚祖先成分的人群的匹配率相差多远？” 通过回答这个问题，我们可以估算出每个印度人群中西欧亚相关祖先成分的比例。

To make these estimates, we measured the degree of the match of a West Eurasian genome to an Indian genome on the one hand and to a Little Andaman Islander genome on the other. The Little Andamanese were crucial here because they are related (albeit distantly) to the ASI but do not have the West Eurasian–related ancestry present in all mainland Indians, so we could use them as a reference point for our analysis. We then repeated the analysis, now replacing the Indian genome with the genome of a person from the Caucasus to measure the match rate we should expect if a genome was entirely of West Eurasian–related ancestry. By comparing the two numbers, we could ask: “How far is each Indian population from what we would expect for a population of entirely West Eurasian ancestry?” By answering this question we could estimate the proportion of West Eurasian–related ancestry in each Indian population.

在本项初步研究以及后续针对更多印度人群的研究中，我们发现印度人群中西欧亚血统的比例从低至20%到高达80%不等。²²这种西欧亚血统在印度人群中的连续分布，正是我们在主成分分析图中观察到的印度人种渐变带（Indian Cline）的成因。无论是最高种姓还是最低种姓，包括生活在种姓制度之外的非印度教部落人口，所有人群都受到了血统混合的影响。

In this initial study and in subsequent studies with larger numbers of Indian groups, we found that West Eurasian–related mixture in India ranges from as low as 20 percent to as high as 80 percent.²² This continuum of West Eurasian–related ancestry in India is the reason for the Indian Cline—the gradient we had seen on our principal components plots. No group is unaffected by mixing, neither the highest nor the lowest caste, including the non-Hindu tribal populations living outside the caste system.

混合比例为我们了解过去的历史事件提供了线索。例如，基因数据暗示了古代ANI和ASI所使用的语言。在印度，使用印欧语系语言的人群通常比使用达罗毗荼语系语言的人群拥有更多的ANI血统，而后者则拥有更多的ASI血统。这表明，ANI可能传播了印欧语系语言，而ASI则传播了达罗毗荼语系语言。

The mixture proportions provided clues about past events. For one thing, the genetic data hinted at the languages spoken by the ancient ANI and ASI. Groups in India that speak Indo-European languages typically have more ANI ancestry than those speaking Dravidian languages, who have more ASI ancestry. This suggested to us that the ANI probably spread Indo-European languages, while the ASI spread Dravidian languages.

基因数据还暗示了古代ANI（平均社会地位较高）和ASI（社会地位较低）的社会地位。平均而言）。在印度种姓制度中，传统上社会地位较高的群体通常比传统上社会地位较低的群体拥有更高比例的ANI（非洲、北印度和印度裔）血统，即使在印度同一个邦，即使所有人都说同一种语言也是如此。 ²³例如，婆罗门（祭司种姓）往往比他们所居住的其他群体拥有更多的ANI血统，即使是说同一种语言的群体。尽管印度也存在一些例外情况，包括一些有据可查的群体社会地位发生转变的案例， ²⁴但这些发现具有统计学意义，表明古代印度的ANI-ASI（非洲、北印度和南印度）血统混合发生在社会分层的背景下。

The genetic data also hinted at the social status of the ancient ANI (higher social status on average) and ASI (lower social status on average). Groups of traditionally higher social status in the Indian caste system typically have a higher proportion of ANI ancestry than those of traditionally lower social status, even within the same state of India where everyone speaks the same language.²³ For example, Brahmins, the priestly caste, tend to have more ANI ancestry than the groups they live among, even those speaking the same language. Although there are groups in India that are exceptions to these patterns, including well-documented cases where whole groups have shifted social status,²⁴ the findings are statistically clear, and suggest that the ANI-ASI mixture in ancient India occurred in the context of social stratification.

如今印度人的基因数据也揭示了男女社会权力差异的历史。大约20%至40%的印度男性和30%至50%的东欧男性拥有一种Y染色体类型，根据携带该类型人群的突变密度推断，这种Y染色体类型在过去6800至4800年间源自同一位男性祖先。 ²⁵与之相反，通过母系遗传的线粒体DNA几乎完全局限于印度，这表明即使在北部地区，线粒体DNA也可能几乎全部来自南亚地区。对此唯一可能的解释是，青铜时代或之后，西欧亚大陆和印度之间发生了大规模的人口迁徙。拥有这种Y染色体类型的男性在繁衍后代方面极其成功，而女性移民对遗传的贡献则小得多。

The genetic data from Indians today also reveal something about the history of differences in social power between men and women. Around 20 to 40 percent of Indian men and around 30 to 50 percent of eastern European men have a Y-chromosome type that, based on the density of mutations separating people who carry it, descends in the last sixty-eight hundred to forty-eight hundred years from the same male ancestor.²⁵ In contrast, the mitochondrial DNA, passed down along the female line, is almost entirely restricted to India, suggesting that it may have nearly all come from the ASI, even in the north. The only possible explanation for this is major migration between West Eurasia and India in the Bronze Age or afterward. Males with this Y chromosome type were extraordinarily successful at leaving offspring while female immigrants made far less of a genetic contribution.

Y染色体和线粒体DNA模式之间的差异最初令历史学家感到困惑。 ²⁶但一种可能的解释是，印度大部分ANI（非洲原住民）的基因输入来自男性。这种性别不对称的人口混合模式令人不安地似曾相识。以非裔美国人为例。他们约20%的欧洲血统来自男性，而男性血统的比例几乎是男性的四倍。²⁷再以哥伦比亚的拉丁裔为例。他们约80%的欧洲血统来自男性，而男性血统的比例更加不平衡（50:1）。²⁸我在第三部分探讨了这对于不同人群之间以及男性和女性之间的关系意味着什么，但共同点是，来自……人群的男性……权力较大的男性倾向于与权力较小的女性交配。令人惊叹的是，基因数据竟然能够揭示过去事件的社会本质如此深刻的信息。

The discrepancy between the Y-chromosome and mitochondrial DNA patterns initially confused historians.²⁶ But a possible explanation is that most of the ANI genetic input into India came from males. This pattern of sex-asymmetric population mixture is disturbingly familiar. Consider African Americans. The approximately 20 percent of ancestry that comes from Europeans derives in an almost four-to-one ratio from the male side.²⁷ Consider Latinos from Colombia. The approximately 80 percent of ancestry that comes from Europeans is derived in an even more unbalanced way from males (a fifty-to-one ratio).²⁸ I explore in part III what this means for the relationships among populations, and between males and females, but the common thread is that males from populations with more power tend to pair with females from populations with less. It is amazing that genetic data can reveal such profound information about the social nature of past events.

哈拉帕文明末期的人口混合

Population Mixture at the Twilight of Harappa

为了理解我们关于人口混合的研究结果在印度历史背景下的意义，我们不仅需要知道人口混合是否发生过，还需要知道人口混合发生的时间。

To understand what our findings about population mixture meant in the context of Indian history, we needed to know not just that population mixture had occurred, but also when.

我们考虑的一种可能性是，我们检测到的混合物是由于大约一万四千年前，上一个冰河时代末期的大规模人类迁徙造成的，当时气候的改善使沙漠变成了适宜居住的土地，并促成了其他环境变化，迫使人们在欧亚大陆上四处迁徙。

One possibility we considered is that the mixtures we had detected were due to great human migrations at the end of the last ice age, after around fourteen thousand years ago, as improving climates changed deserts into habitable land and contributed to other environmental change that drove people hither and yon across the landscape of Eurasia.

第二种可能性是，这些混合物反映了近东农民向南亚的迁徙，这种迁徙可能是近东农业在九千年前传播到印度河流域的一种可能解释。

A second possibility is that the mixtures reflected movements of farmers of Near Eastern origin into South Asia, a migration that could be a possible explanation for the spread of Near Eastern farming into the Indus Valley after nine thousand years ago.

第三种可能性是，这些混血发生在过去四千年间，与如今在印度和欧洲使用的印欧语系语言的传播有关。这种可能性暗示了《梨俱吠陀》中描述的事件。然而，即使混血发生在四千年之后，也完全有可能发生在已在此定居的人群之间，其中一个人群可能在几个世纪甚至几千年前从西欧亚大陆迁徙到该地区，但尚未与印度土著居民（ASI）通婚。

A third possibility is that the mixtures occurred in the last four thousand years associated with the dispersal of Indo-European languages that are spoken today in India as well as in Europe. This possibility hints at events described in the Rig Veda. However, even if mixture occurred after four thousand years ago, it is entirely possible that it took place between already-resident populations, one of which had migrated to the area from West Eurasia some centuries or even millennia earlier but had not yet interbred with the ASI.

这三种可能性都涉及从西欧亚大陆向印度的迁徙。尽管辛格和坦加拉杰曾提出从印度向西迁徙至欧洲的可能性，以此解释亚洲印度人与西欧亚人群之间的亲缘关系，但我一直认为，鉴于当今绝大多数西欧亚人身上没有任何亚洲印度人血统的痕迹，以及印度在当今具有西欧亚相关血统人群分布中极其特殊的地理位置，共同的祖先成分可能反映了古代从北方或西方迁徙到南亚的人群。通过测定混血人群的年代，我们可以获得更确切的信息。

All three of the possibilities involve migration at some point from West Eurasia into India. Although Singh and Thangaraj entertained the possibility of a migration out of India and into points as far west as Europe to explain the relatedness between the ANI and West Eurasian populations, I have always thought, based on the absence of any trace of ASI ancestry in the great majority of West Eurasians today and the extreme geographic position of India within the present-day distribution of peoples bearing West Eurasian–related ancestry, that the shared ancestry likely reflected ancient migrations into South Asia from the north or west. By dating the mixture, we could obtain more concrete information.

确定起源日期的挑战促使我们开发了一系列新方法。我们的方法是利用这样一个事实：在ANI和ASI混合后的第一代，他们的后代将完全拥有ANI或ASI血统的染色体。在随后的每一代中，随着个体将父母的染色体组合起来形成他们遗传给后代的染色体，ANI和ASI血统的片段会逐渐断裂，每条染色体每代都会出现一到两个断裂点。通过测量当今印度人ANI或ASI血统片段的典型长度，并确定需要多少代才能将其缩短到目前的长度，我实验室的研究生Priya Moorjani成功地估算出了起源日期。 ²⁹

The challenge of getting a date prompted us to develop a series of new methods. Our approach was to take advantage of the fact that in the first generation after the ANI and ASI mixed, their offspring would have had chromosomes of entirely ANI or ASI ancestry. In each subsequent generation, as individuals combined their mother’s and father’s chromosomes to produce the chromosome they passed on to their offspring, the stretches of ANI and ASI ancestry would have broken up, with one or two breakpoints per generation per chromosome. By measuring the typical size of stretches of ANI or ASI ancestry in Indians today, and determining how many generations would be needed to chop them down to their current size, Priya Moorjani, a graduate student in my laboratory, succeeded in estimating a date.²⁹

我们发现，我们分析的所有印度人群的ANI-ASI混合年代都在4000至2000年前之间，其中印欧语系人群的混合年代平均比达罗毗荼语系人群更近。达罗毗荼语系人群更早的混合年代让我们感到惊讶。我们原本预期，最早的混合年代会出现在北部的印欧语系人群中，因为人们推测混合最早发生在那里。后来我们意识到，达罗毗荼语系人群更早的混合年代其实是合理的，因为人们现在的居住地并不一定反映他们过去的居住地。假设印度的第一次混合发生在大约4000年前的北部，随后随着先前定居的人群和具有更多西欧亚血统的人群在边界地带反复接触，印度北部又发生了多次混合浪潮。北印度最早的混血人群很可能在数千年间与南印度人群融合或迁徙，因此，如今南印度人群的混血年代应为第一轮混血的年代。之后，西欧亚相关人群与北印度人群的混血浪潮，则会导致如今北印度人群的平均混血年代比南印度人群更晚。对基因数据的深入分析证实了ANI相关基因多次向北方扩散的理论。在印度北部人群中，我们发现了一些源自ANI的短片段DNA，同时也发现了一些较长的ANI衍生DNA片段，这必然反映了近期与ASI血统较少或没有ASI血统的人群的基因混合^。30

We found that all Indian groups we analyzed had ANI-ASI mixture dates between four thousand and two thousand years ago, with Indo-European-speaking groups having more recent mixture dates on average than Dravidian-speaking groups. The older mixture dates in Dravidian speakers surprised us. We had expected that the oldest mixtures would be found in Indo-European-speaking groups of the north, as it is presumably there that the mixture first occurred. We then realized that an older date in Dravidians actually makes sense, as the present-day locations of people do not necessarily reflect their past locations. Suppose that the first round of mixture in India happened in the north close to four thousand years ago, and was followed by subsequent waves of mixture in northern India as previously established populations and people with much more West Eurasian ancestry came into contact repeatedly along a boundary zone. The people who were the products of the first mixtures in northern India could plausibly, over thousands of years, have mixed with or migrated to southern India, and thus the dates in southern Indians today would be those of the first round of mixture. Later waves of mixture of West Eurasian–related people into northern Indian groups would then cause the average date of mixture estimated in northern Indians today to be more recent than in southern Indians. A hard look at the genetic data confirms the theory of multiple waves of ANI-related mixture into the north. Interspersed among the short stretches of ANI-derived DNA we find in northern Indians, we also find quite long stretches of ANI-derived DNA, which must reflect recent mixtures with people of little or no ASI ancestry.³⁰

值得注意的是，我们观察到的模式与以下假设相符：现代印度某些族群历史上发生的所有ANI和ASI血统混合都发生在过去四千年内。这意味着大约四千年前印度的人口结构与今天截然不同。在此之前，印度人口相对单一，但此后，印度经历了剧烈的血统混合，几乎影响了所有族群。

Remarkably, the patterns we observed were consistent with the hypothesis that all of the mixture of ANI and ASI ancestry that occurred in the history of some present-day Indian groups happened within the last four thousand years. This meant that the population structure of India before around four thousand years ago was profoundly different from what it is today. Before then, there were unmixed populations, but afterward, there was convulsive mixture in India, which affected nearly every group.

因此，在四千年到三千年前——正值印度河文明衰落和《梨俱吠陀》成书之际——此前各自隔离的人群发生了深刻的融合。如今在印度，说着不同语言、来自不同社会阶层的人们拥有不同比例的ANI（亚洲、北印度和印度裔）血统。如今，印度的ANI血统更多地来源于男性而非女性。这种模式完全符合预期：一个印欧语系民族在四千年前掌握了政治和社会权力，并在等级分明的社会中与当地居民融合，来自权力阶层的男性比来自弱势群体的男性更容易找到伴侣。

So between four thousand and three thousand years ago—just as the Indus Civilization collapsed and the Rig Veda was composed—there was a profound mixture of populations that had previously been segregated. Today in India, people speaking different languages and coming from different social statuses have different proportions of ANI ancestry. Today, ANI ancestry in India derives more from males than from females. This pattern is exactly what one would expect from an Indo-European-speaking people taking the reins of political and social power after four thousand years ago and mixing with the local peoples in a stratified society, with males from the groups in power having more success in finding mates than those from the disenfranchised groups.

种姓制度的古老性

The Antiquity of Caste

为什么经过数千年的历史，这些古代事件的遗传标记还没有变得面目全非？

How is it that the genetic marks of these ancient events have not been blurred beyond recognition after thousands of years of history?

传统印度社会最显著的特征之一是种姓制度——这种社会分层体系决定了人们的婚姻对象以及他们在社会中享有的特权和角色。种姓制度的压迫性催生了三大宗教——耆那教、佛教和锡克教——作为对种姓制度的反抗，这些宗教都为人们提供了逃避现实的庇护所。种姓制度。伊斯兰教在印度的成功也得益于它为社会地位低下的群体提供了一条出路，这些人纷纷皈依莫卧儿统治者的新宗教。1947年，随着民主印度的诞生，种姓制度被废除，但它至今仍然影响着人们的社交和婚姻选择。

One of the most distinctive features of traditional Indian society is caste—the system of social stratification that determines whom one can marry and what privileges and roles one has in society. The repressive nature of caste has spawned in reaction major religions—Jainism, Buddhism, and Sikhism—each of which offered refuge from the caste system. The success of Islam in India was also fueled by the escape it provided for low-social-status groups that converted en masse to the new religion of the Mughal rulers. Caste was outlawed in 1947 with the birth of democratic India, but it still shapes whom people choose to socialize with and marry today.

从社会学角度来说，种姓是指一个群体通过特定的经济角色与群体外的人进行经济互动，但通过族内通婚（禁止与外族通婚）在社会上自我隔离。我的祖先来自东北欧的犹太人，在18世纪末开始的“犹太人解放运动”之前，在并非所有群体都是种姓的地区，犹太人属于一个种姓。犹太人为他们所居住的地区提供经济服务，例如放贷、售卖酒水、经商和手工艺。当时的犹太教徒和现在一样，通过饮食规则（犹太教规）、独特的服饰、身体改造（男性割礼）以及禁止与外族通婚等方式在社会上自我隔离。

A sociological definition of a caste is a group that interacts economically with people outside it (through specialized economic roles), but segregates itself socially through endogamy (which prevents people from marrying outsiders). Jews in northeastern Europe, from whom I descend, were, prior to the “Jewish emancipation” beginning in the late eighteenth century, a caste in lands where not all groups were castes. Jews served an economic function as moneylenders, liquor vendors, merchants, and craftspeople for the population within which they lived. Religious Jews then as now segregated themselves socially through dietary rules (kosher laws), distinctive dress, body modification (circumcision of males), and strictures against marrying outsiders.

印度的种姓制度分为两个层次：瓦尔纳（Varna）和贾蒂（Jati）。31 瓦尔纳制度将整个^社会至少分为四个等级：最高等级是祭司阶层（婆罗门）和武士阶层（刹帝利）；中间等级是商人、农民和工匠阶层（吠舍）；最低等级是劳动阶层（首陀罗）。此外，还有旃陀罗或达利特人——“表列种姓”——他们被认为地位极低，被视为“不可接触者”，被排除在正常社会之外。最后，还有“表列部落”，这是印度政府对非印度教徒（既非穆斯林也非基督徒）的官方称呼。种姓制度是传统印度教社会的重要组成部分，在《梨俱吠陀》之后编纂的宗教经典（吠陀经）中有详细描述。

Caste in India is organized at two levels, varna and jati.³¹ The varna system involves stratification of all of society into at least four ranks: at the top the priestly group (Brahmins) and the warrior group (Kshatriyas); in the middle the merchants, farmers, and artisans (Vaishya); and finally the lower castes (Shudras), who are laborers. There are also the Chandalas or Dalits—“Scheduled Castes”—people who are considered so low that they are “untouchable” and excluded from normal society. Finally, there are the “Scheduled Tribes,” the official Indian government name for people outside Hinduism who are neither Muslim nor Christian. The caste system is a deep part of traditional Hindu society and is described in detail in the religious texts (Vedas) that were composed subsequent to the Rig Veda.

印度以外的人很少了解种姓制度，它远比印度的种姓制度复杂得多，至少包含四千六百个，甚至据一些统计约有四万个内部通婚群体。 ³²每个群体在瓦尔纳制度中都被赋予特定的等级，但严格而复杂的内部通婚规则使得大多数不同种姓的人即使处于同一瓦尔纳等级，也无法通婚。此外，显然在过去，整个种姓群体都曾经历过类似的情况。他们的种姓等级发生了变化。例如，古吉尔种姓（印度西北部古吉拉特邦即以此种姓命名）的等级因居住地不同而有所差异，这可能反映出在某些地区，古吉尔人成功地争取到了提升其^种姓在种姓等级制度中地位的机会。33

The jati system, which few people outside India understand, is much more complicated, and involves a minimum of forty-six hundred and by some accounts around forty thousand endogamous groups.³² Each is assigned a particular rank in the varna system, but strong and complicated endogamy rules prevent people from most different jatis from mixing with each other, even if they are of the same varna level. It is also clear that in the past, whole jati groups have changed their varna ranks. For example, the Gujjar jati (from which the state of Gujarat in northwest India takes its name) have a variety of ranks depending on where in India they live, which is likely to reflect the fact that in some regions, Gujjars have successfully made the case to raise the status of their jati within the varna hierarchy.³³

种姓（Varna）和种姓（Jati）之间的关系一直是人们争论不休的谜团。人类学家伊拉瓦蒂·卡尔维（Irawati Karve）提出的一个假说是，数千年前，印度人生活在互不通婚的部落群体中，这与当今世界其他地区的部落群体非常相似。 ³⁴随后，政治精英（如祭司、国王和商人）巩固了他们在社会体系顶端的地位，建立了一种等级分明的社会体系。在这个体系中，部落群体以劳动群体的形式融入社会，而首陀罗（Shudra）和达利特（Dalit）则处于社会底层。部落组织由此与社会分层体系融合，形成了早期的种姓（Jati）。最终，种姓结构渗透到社会更高阶层，因此今天存在着许多不同种姓的群体。这些古老的部落群体通过种姓制度和内婚规则保留了其独特性。

How the varna and jati relate to each other is a much-debated mystery. One hypothesis suggested by the anthropologist Irawati Karve is that thousands of years ago, Indian peoples lived in effectively endogamous tribal groups that did not mix, much like tribal groups in other parts of the world today.³⁴ Political elites then ensconced themselves at the top of the social system (as priests, kings, and merchants), creating a stratified system in which the tribal groups were incorporated into society in the form of laboring groups that remained at the bottom of society as Shudras and Dalits. The tribal organization was thus fused with the system of social stratification to form early jatis, and eventually the jati structure percolated up to the higher ranks of society, so that today there are many jatis of higher as well as of lower castes. These ancient tribal groups have preserved their distinctiveness through the caste system and endogamy rules.

另一种假设是，严格的族内通婚规则其实并不古老。种姓制度的理论无疑历史悠久，正如古代印度教经典《摩奴法典》中所描述的那样。《摩奴法典》成书于《梨俱吠陀》之后数百年，它对瓦尔纳（varna）等级社会分层制度及其内部无数的贾蒂（jati）群体进行了详尽的描述。该法典将整个制度置于宗教框架之下，并将其存在合理化为自然秩序的一部分。然而，以人类学家尼古拉斯·迪克斯（Nicholas Dirks）为首的修正主义历史学家认为，事实上，严格的族内通婚制度并非古代印度的惯例，而是英国殖民主义的产物。^迪克斯及其同事指出，为了有效地统治印度，英国自18世纪起推行的政策是强化种姓制度，从而在印度社会中为英国殖民者开辟了一个新的种姓群体，为其自身创造了一个天然的位置。为了实现这一目标，英国人在印度一些种姓制度并不十分重要的地区加强了种姓制度，并致力于协调不同地区的种姓规则。迪克斯认为，这些努力表明，如今种姓制度中表现出的严格的族内通婚限制，在实践中可能并没有看起来那么古老。

An alternative hypothesis is that strong endogamy rules are not very old at all. The theory of the caste system is undeniably old, as it is described in the ancient Law Code of Manu, a Hindu text composed some hundreds of years after the Rig Veda. The Law Code of Manu describes in exquisite detail the varna system of ranked social stratification, and within it the innumerable jati groups. It puts the whole system into a religious framework, justifying its existence as part of the natural order of life. However, revisionist historians, led by the anthropologist Nicholas Dirks, have argued that in fact strong endogamy was not practiced in ancient India, but instead is largely an innovation of British colonialism.³⁵ Dirks and colleagues showed how, as a way of effectively ruling India, British policy beginning in the eighteenth century was to strengthen the caste system, carving out a natural place within Indian society for British colonialists as a new caste group. To achieve this, the British strengthened the institution of caste in parts of India where it was not very important, and worked to harmonize caste rules across different regions. Given these efforts, Dirks suggested that strong endogamy restrictions as manifested in today’s castes might not be as old in practice as they seem.

为了解种姓与真实遗传模式的对应程度，我们基于突变频率的差异，检验了我们掌握数据的每个种姓与其他所有种姓之间的分化程度。 ³⁶我们发现，这种分化程度至少是地理距离相近的欧洲人群分化程度的三倍。这无法用人群间ANI祖先的差异、人口来源地（印度境内）的差异或社会地位的差异来解释。即使比较符合上述标准的人群，我们也发现印度人群间的遗传分化程度远高于欧洲人群。

To understand the extent to which the jatis corresponded to real genetic patterns, we examined the degree of differentiation of each jati from which we had data with all others based on differences in mutation frequencies.³⁶ We found that the degree of differentiation was at least three times greater than that among European groups separated by similar geographic distances. This could not be explained by differences in ANI ancestry among groups, or differences in the region within India from which the population came, or differences in social status. Even comparing pairs of groups matched according to these criteria, we found that the degree of genetic differentiation among Indian groups was many times larger than that in Europe.

这些发现使我们推测，如今许多印度族群可能是人口瓶颈效应的产物。人口瓶颈效应是指相对较少的个体生育大量后代，而这些后代也生育大量后代，并由于社会或地理障碍而与周围人群在基因上保持隔离。欧洲血统人群历史上著名的人口瓶颈效应包括：芬兰人口主要祖先的形成（约两千年前）、如今德系犹太人祖先的很大一部分形成（约六百年前），以及最终迁徙到北美的宗教异见者（如胡特尔派和阿米什派）的大部分祖先的形成（约三百年前）。在所有这些案例中，少数个体的高生育率导致这些个体携带的罕见突变在其后代中的频率增加。 ³⁷

These findings led us to surmise that many Indian groups today might be the products of population bottlenecks. These occur when relatively small numbers of individuals have many offspring and their descendants too have many offspring and remain genetically isolated from the people who surround them due to social or geographic barriers. Famous population bottlenecks in the history of people of European ancestry include the ones that contributed most of the ancestry of the Finnish population (around two thousand years ago), a large fraction of the ancestry of today’s Ashkenazi Jews (around six hundred years ago), and most of the ancestry of religious dissenters such as Hutterites and Amish who eventually migrated to North America (around three hundred years ago). In each case, a high reproductive rate among a small number of individuals caused the rare mutations carried in those individuals to rise in frequency in their descendants.³⁷

我们在印度寻找人口瓶颈的蛛丝马迹，并发现了它们：同一群体中两两个体之间存在相同的长片段序列。对此，唯一可能的解释是，这两个个体都拥有几千年来携带该DNA片段的共同祖先。此外，共享DNA片段的平均长度揭示了这位共同祖先生活的年代，因为共享的DNA片段长度与已知的DNA片段长度相同。在每一代中，基因片段都会通过重组过程以固定的速度断裂。

We looked for the telltale signs of population bottlenecks in India and found them: identical long stretches of sequence between pairs of individuals within the same group. The only possible explanation for such segments is that the two individuals descend from an ancestor in the last few thousand years who carried that DNA segment. What’s more, the average size of the shared DNA segments reveals how long ago in the past that shared ancestor lived, as the shared segments break up at a regular rate in each generation through the process of recombination.

基因数据清晰地揭示了这一现象。大约三分之一的印度族群经历了与芬兰人或德系犹太人一样强烈甚至更严重的人口瓶颈效应。后来，我们与 Thangaraj 合作，收集了来自印度各地250 多个种姓群体的基因数据，并在更大的数据集上证实了这一发现。 ³⁸

The genetic data told a clear story. Around a third of Indian groups experienced population bottlenecks as strong or stronger than the ones that occurred among Finns or Ashkenazi Jews. We later confirmed this finding in an even larger dataset that we collected working with Thangaraj: genetic data from more than 250 jati groups spread throughout India.³⁸

印度的许多人口瓶颈事件也发生得非常久远。我们发现的最引人注目的例子之一是印度南部安得拉邦的吠舍种姓，这是一个拥有约五百万人口的中等种姓群体，我们根据同一群体中个体间共享的群体大小，推断出其人口瓶颈发生在三千年前到两千年前。

Many of the population bottlenecks in India were also exceedingly old. One of the most striking we discovered was in the Vysya of the southern Indian state of Andhra Pradesh, a middle caste group of approximately five million people whose population bottleneck we could date (from the size of segments shared between individuals of the same population) to between three thousand and two thousand years ago.

对吠舍人祖先如此强烈的种群瓶颈现象的观察令人震惊。这意味着在种群瓶颈之后，吠舍人的祖先一直保持着严格的族内通婚，数千年来几乎没有与其他族群进行基因交流。即使每代只有1%的基因流入吠舍人，也会抹去种群瓶颈留下的基因信号。吠舍人的祖先并非生活在地理隔离区。相反，他们与印度人口稠密地区的其他族群比邻而居。尽管与其他族群距离很近，吠舍人的族内通婚规则和群体认同感却非常强烈，以至于他们与邻近族群保持着严格的社会隔离，并将这种社会隔离的文化传承给了每一代后代。

The observation of such a strong population bottleneck among the ancestors of the Vysya was shocking. It meant that after the population bottleneck, the ancestors of the Vysya had maintained strict endogamy, allowing essentially no genetic mixing into their group for thousands of years. Even an average rate of influx into the Vysya of as little as 1 percent per generation would have erased the genetic signal of a population bottleneck. The ancestors of the Vysya did not live in geographic isolation. Instead, they lived cheek by jowl with other groups in a densely populated part of India. Despite proximity to other groups, the endogamy rules and group identity in the Vysya have been so strong that they maintained strict social isolation from their neighbors, and transmitted that culture of social isolation to each and every subsequent generation.

吠舍人并非个例。我们分析的群体中有三分之一都呈现出类似的信号，这意味着印度存在成千上万个类似的群体。事实上，我们甚至可能低估了受长期严格内婚制影响的印度群体的比例。一个群体要表现出这种信号，就必须经历过人口瓶颈。那些起源于众多创始者却始终保持严格内婚制的群体，我们的统计数据无法检测到。正如迪克斯所言，长期内婚制并非殖民主义的产物，而是当今印度社会中普遍存在的现象。种姓制度在数千年来一直发挥着极其重要的作用。

And the Vysya were not unique. A third of the groups we analyzed gave similar signals, implying thousands of groups in India like this. Indeed, it is even possible that we were underestimating the fraction of groups in India affected by strong long-term endogamy. To show a signal, a group needed to have gone through a population bottleneck. Groups that descended from a larger number of founders but nevertheless maintained strict endogamy ever since would go undetected by our statistics. Rather than an invention of colonialism as Dirks suggested, long-term endogamy as embodied in India today in the institution of caste has been overwhelmingly important for millennia.

了解印度历史的这一特点让我感触颇深。当我开始研究印度族群时，我的身份是阿什肯纳兹犹太人，一个西欧亚大陆古老种姓的成员。我对自己的身份感到不安，但并不清楚究竟不安在哪里。我对印度的研究让我逐渐清晰地认识到这种不安。我的犹太背景是无法回避的。我的父母非常重视世俗世界，但他们自己却成长于一个宗教氛围浓厚的社区，是逃离欧洲迫害的难民的后代，这使他们拥有强烈的民族认同感。在我成长的过程中，我们家一直遵循犹太教的饮食规则——我相信我的父母这样做，部分原因是希望他们的家人来我们家吃饭时也能感到自在——我上了九年的犹太学校，并在耶路撒冷度过了许多个暑假。从父母、祖父母和堂表兄弟姐妹那里，我深深地感受到一种与众不同的意识——一种我们群体特殊的感受——以及如果我与非犹太人结婚会令家人失望和难堪的认知（我知道这种观念也对我的兄弟姐妹产生了深远的影响）。当然，我担心让家人失望的程度，与在印度，许多人因与非犹太人结婚而遭受的羞辱、孤立和暴力相比，简直微不足道。然而，作为一名犹太人，我的视角让我对印度数千年历史中那些跨越种族界限、因种姓制度而被迫扼杀的罗密欧与朱丽叶式的爱情深感同情。我的犹太身份也让我从切身层面理解了这种制度是如何成功地延续至今的。

Learning this feature of Indian history had a strong resonance for me. When I started my work on Indian groups, I came to it as an Ashkenazi Jew, a member of an ancient caste of West Eurasia. I was uncomfortable with my affiliation but did not have a clear sense of what I was uncomfortable about. My work on India crystallized my discomfort. There is no escaping my background as a Jew. I was raised by parents whose highest priority was being open to the secular world, but they themselves had been raised in a deeply religious community and were children of refugees from persecution in Europe that left them with a strong sense of ethnic distinctiveness. When I was growing up, we followed Jewish dietary rules at home—I believe my parents did so in part in the hope that their own families would feel comfortable eating at our house—and I went for nine years to a Jewish school and spent many summers in Jerusalem. From my parents as well as from my grandparents and cousins I imbibed a strong sense of difference—a feeling that our group was special—and a knowledge that I would cause disappointment and embarrassment if I married someone non-Jewish (a conviction that I know also had a powerful effect on my siblings). Of course, my concern about disappointing my family is nothing compared to the shame, isolation, and violence that many expect in India for taking a partner outside their group. And yet my perspective as a Jew made me empathize strongly with all the likely Romeos and Juliets over thousands of years of Indian history whose loves across ethnic lines have been quashed by caste. My Jewish identity also helped me to understand on a visceral level how this institution had successfully perpetuated itself for so long.

数据显示，印度内部不同种姓群体之间的基因差异在很多情况下是真实存在的，这要归因于次大陆悠久的族内通婚历史。人们往往认为拥有超过13亿人口的印度人口数量极其庞大，事实上，许多印度人和外国人也都这么认为。但从基因学的角度来看，这种看法是错误的。汉族人口确实庞大，他们数千年来一直自由通婚。相比之下，印度几乎没有人口规模非常大的族群，而且居住在同一村庄的印度种姓群体之间的基因分化程度通常是北欧人和南欧人之间基因分化程度的两到三倍。 ³⁹事实上，印度是由大量小族群组成的。

What the data were showing us was that the genetic distinctions among jati groups within India were in many cases real, thanks to the long-standing history of endogamy in the subcontinent. People tend to think of India, with its more than 1.3 billion people, as having a tremendously large population, and indeed many Indians as well as foreigners see it this way. But genetically, this is an incorrect way to view the situation. The Han Chinese are truly a large population. They have been mixing freely for thousands of years. In contrast, there are few if any Indian groups that are demographically very large, and the degree of genetic differentiation among Indian jati groups living side by side in the same village is typically two to three times higher than the genetic differentiation between northern and southern Europeans.³⁹ The truth is that India is composed of a large number of small populations.

印度遗传学、历史与健康

Indian Genetics, History, and Health

经历过人口瓶颈效应的欧洲裔群体——例如德系犹太人、芬兰人、胡特尔派教徒、阿米什人、萨格奈-圣让湖地区的法裔加拿大人等等——一直是医学研究人员持续深入且卓有成效的研究对象。由于人口瓶颈效应，原本携带在创始个体身上的罕见致病突变频率显著增加。当一个人只从父母一方遗传到这些罕见突变时，它们通常是无害的（因为它们是隐性突变，需要两个拷贝才会致病）；但如果一个人从父母双方都遗传到这些突变，则可能致命。然而，一旦这些突变由于人口瓶颈效应而频率增加，群体中的个体就很有可能从父母双方都遗传到相同的突变。例如，德系犹太人中泰-萨克斯病的发病率很高，这种毁灭性疾病会导致脑部退化，并在出生后的最初几年内导致死亡。我的一位堂兄出生几个月后便因泽尔维格综合征（一种德系犹太人特有的疾病）夭折；我母亲的一位堂兄也因莱利-戴综合征（又称家族性自主神经功能障碍）早逝，这也是一种德系犹太人特有的疾病。目前已发现数百种此类疾病，并在包括德系犹太人在内的欧洲人群中鉴定出致病基因。这些发现带来了重要的生物学见解，并在少数情况下促成了对抗受损基因影响的药物的研发。

The groups of European ancestry that have experienced strong population bottlenecks—Ashkenazi Jews, Finns, Hutterites, Amish, French Canadians of the Saguenay–Lac-St.-Jean region, and others—have been the subject of endless and productive study by medical researchers. Because of their population bottlenecks, rare disease-causing mutations that happened to have been carried in the founder individuals have dramatically increased in frequency. Rare mutations that are innocuous when a person inherits a copy from only one of their parents—they act recessively, which means that two copies are required to cause disease—can be lethal when a person inherits copies from both parents. However, once these mutations increase in frequency due to a population bottleneck, there is an appreciable chance that individuals in the population will inherit the same mutation from both of their parents. For example, in Ashkenazi Jews there is a high incidence of the devastating disease of Tay-Sachs, which causes brain degeneration and death within the first few years of life. One of my first cousins died within months of birth due to an Ashkenazi founder disease called Zellweger syndrome, and one of my mother’s first cousins died young of Riley-Day syndrome, or familial dysautonomia, another Ashkenazi founder disease. Hundreds of such diseases have been identified, and the responsible genes have been identified in European founder populations, including Ashkenazi Jews. These findings have led to important biological insights and in a few cases to the development of drugs that counteract the effect of the damaged genes.

当然，印度的这类人群数量要多得多。由于印度人口众多，且约有三分之一的印度种姓群体（jati ）的祖先经历了与德系犹太人或芬兰人一样甚至更严重的人口瓶颈，因此印度人口增长经历了严重的瓶颈效应。寻找导致这些印度群体疾病的基因，有可能识别出数千种疾病的风险因素。尽管目前尚无人进行系统性的研究，但一些此类案例已为人所知。例如，已知维夏人（Vysya）在术前使用肌肉松弛剂后，出现持续性肌肉麻痹的比例很高。因此，印度的临床医生知道不应给维夏血统的人使用此类药物。这种情况是由于部分维夏人体内丁基胆碱酯酶蛋白水平较低所致。基因研究表明，这种疾病是由一种隐性突变引起的，该突变在维夏人中的发生率约为20%，远高于其他印度群体，这可能是因为维夏人的祖先之一携带了这种突变。⁴⁰这种频率非常高，以至于大约 4% 的 Vysya 人会出现两个拷贝的突变，导致携带突变并接受麻醉的人出现灾难性反应。

India, of course, has far more people who belong to groups that experienced strong bottlenecks, as the country’s population is huge, and as around one-third of Indian jati groups descend from bottlenecks as strong or stronger than those that occurred in Ashkenazi Jews or Finns. Searches for the genes responsible for disorders in these Indian groups therefore have the potential to identify risk factors for thousands of diseases. Despite the fact that no one has systematically looked, a few such cases are already known. For example, the Vysya are known to have a high rate of prolonged muscle paralysis in response to muscle relaxants given prior to surgery. As a result, clinicians in India know not to give these drugs to people of Vysya ancestry. The condition is due to low levels of the protein butylcholinesterase in some Vysya. Genetic work has shown that this condition is due to a recessively acting mutation that occurs at about 20 percent frequency in the Vysya, a far higher rate than in other Indian groups, presumably because the mutation was carried in one of the Vysya’s founders.⁴⁰ This frequency is sufficiently high that the mutation occurs in two copies in about 4 percent of the Vysya, causing disastrous reactions for people who carry the mutation and go under anesthesia.

正如吠舍种姓的例子所示，印度的历史为生物学发现提供了重要的契机，因为借助现代基因技术，寻找罕见隐性疾病的致病基因成本低廉。只需找到某个种姓群体中患有该疾病的少数人，并对其基因组进行测序即可。基因方法可以识别出印度数千个种姓群体中哪些群体经历过严重的人口瓶颈。当地医生和助产士可以识别出在特定群体中高发的综合征。当地医生接生过成千上万的婴儿，他们肯定知道某些疾病和畸形在某些群体中的发病率高于其他群体。这些信息足以收集少量血液样本进行基因分析。一旦获得这些样本，寻找致病基因的基因工作就变得简单明了。

As the Vysya example demonstrates, the history of India presents an important opportunity for biological discovery, as finding genes for rare recessive diseases is cheap with modern genetic technology. All it takes is access to a small number of people in a jati group with the disease, whose genomes can then be sequenced. Genetic methods can identify which of the thousands of groups in India have experienced strong population bottlenecks. Local doctors and midwives can identify syndromes that occur at high rates in specific groups. It is surely the case that local doctors, having delivered thousands of babies, will know that certain diseases and malformations occur more frequently in some groups than in others. This is all the information one needs to collect a handful of blood samples for genetic analysis. Once these samples are in hand, the genetic work to find the responsible genes is straightforward.

在印度，通过罕见隐性疾病调查来改变医学现状的机会尤其巨大，因为包办婚姻非常普遍。尽管我对婚姻限制感到不适，但包办婚姻在印度却是不争的事实。在印度，许多犹太社群——就像在极端正统犹太社群中一样——都采用这种方式。我的几位阿什肯纳兹犹太正统社群的堂兄弟姐妹就是通过这种方式找到了伴侣。在这个宗教社群中，约瑟夫·埃克斯坦拉比在1983年创立了一个基因检测机构。此前，他的四个孩子都因泰-萨克斯病去世。该机构几乎使许多隐性遗传疾病绝迹。^在美国和以色列的许多正统犹太教高中，几乎所有青少年都会接受基因检测，以确定他们是否携带少数几种在阿什肯纳兹犹太社群中常见的罕见隐性致病基因突变。如果他们是携带者，媒人绝不会将他们介绍给其他携带相同突变的青少年。印度完全有机会效仿，但与影响几十万人的美国不同，这种方法在印度可能会影响数亿人。

The opportunities for making a medical difference in India through surveys of rare recessive disease are particularly great because arranged marriage is very common. Much as I find restrictions on marriage discomfiting, arranged marriages are a fact in numerous communities in India—as they are in the ultra-Orthodox Jewish community. A number of my own first cousins in the Ashkenazi Jewish Orthodox community have found their spouses that way. In this religious community, a genetic testing organization founded by Rabbi Josef Ekstein in 1983, after he lost four of his own children to Tay-Sachs, has driven many recessive diseases almost to extinction.⁴¹ In many Orthodox religious high schools in the United States and Israel, nearly all teenagers are tested for whether they are carriers of the handful of rare recessive disease-causing mutations that are common in the Ashkenazi Jewish community. If they are carriers, they are never introduced by matchmakers to other teenagers carrying the same mutation. There is every opportunity to do the same in India, but instead of affecting a few hundred thousand people, in India the approach could have an impact on hundreds of millions.

两个次大陆的故事：

印度与欧洲的平行历史

A Tale of Two Subcontinents:

The Parallel History of India and Europe

直到 2016 年，印度人群的基因研究主要集中在 ANI 和 ASI 这两个人群上：这两个人群以不同的比例混合，产生了如今仍然生活在印度的各种族群。

Up until 2016, the genetic studies of Indian groups focused on the ANI and the ASI: the two populations that mixed in different proportions to produce the great diversity of endogamous groups still living in India today.

但这种情况在2016年发生了改变，当时包括我们实验室在内的几个实验室发表了来自世界上最早一些农民的首个全基因组古代DNA数据。这些人生活在距今11000至8000年前，分布在今天的以色列、约旦、安纳托利亚和伊朗地区。 ⁴²当我们研究这些近东早期农民与现代人的亲缘关系时，我们发现现代欧洲人与来自安纳托利亚的早期农民有着很强的基因亲缘性，这与9000年前安纳托利亚农民向欧洲的迁徙相吻合。现代印度人与古代伊朗农民有着很强的亲缘性，这表明9000年前近东农业向东扩张至印度河流域对现代人产生了同样重要的影响。印度人口。43^但我们的研究也表明，当今印度人与古代草原牧民有着很强的基因亲缘关系。伊朗农业扩张对印度人口产生影响的基因证据，如何与草原扩张的证据相协调呢？这种情况让我们想起几年前在欧洲的发现：如今的欧洲人口不仅是本土狩猎采集者和迁徙农民的混合体，还包括起源于草原的第三个主要群体。

But this changed in 2016, when several laboratories, including mine, published the first genome-wide ancient DNA from some of the world’s earliest farmers, people who lived between eleven thousand and eight thousand years ago in present-day Israel, Jordan, Anatolia, and Iran.⁴² When we studied how these early farmers of the Near East were related to people living today, we found that present-day Europeans have strong genetic affinity to early farmers from Anatolia, consistent with a migration of Anatolian farmers into Europe after nine thousand years ago. Present-day people from India have a strong affinity to ancient Iranian farmers, suggesting that the expansion of Near Eastern farming eastward to the Indus Valley after nine thousand years ago had as important an impact on the population of India.⁴³ But our studies also revealed that present-day people in India have strong genetic affinities to ancient steppe pastoralists. How could the genetic evidence of an impact of an Iranian farming expansion on the population of India be reconciled with the evidence of steppe expansions? The situation was reminiscent of what we had found a couple of years before in Europe, where today’s populations are a mixture not just of indigenous hunter-gatherers and migrant farmers, but also of a third major group with an origin in the steppe.

为了深入了解，我实验室的约瑟夫·拉扎里迪斯（Iosif Lazaridis）建立了现代印度人群的数学模型，认为他们是与小安达曼岛居民、古代伊朗农民和古代草原居民相关的群体的混合体。他发现，印度几乎所有人群都拥有这三个群体的血统。⁴⁴尼克·帕特森（Nick Patterson）随后整合了近150个现代印度人群的数据，建立了一个统一的模型，从而能够精确估算这三个祖先群体对现代印度人的贡献。

To gain some insight, Iosif Lazaridis in my laboratory wrote down mathematical models for present-day Indian groups as mixtures of populations related to Little Andaman Islanders, ancient Iranian farmers, and ancient steppe peoples. What he found is that almost every group in India has ancestry from all three populations.⁴⁴ Nick Patterson then combined the data from almost 150 present-day Indian groups to come up with a unified model that allowed him to obtain precise estimates of the contribution of these three ancestral populations to present-day Indians.

帕特森推断，如果一个人群完全由安达曼-尼罗河-印度人（ANI）血统构成——即不包含任何安达曼人相关血统——那么他们的血统构成应该是伊朗农民血统和草原牧民血统的混合体。但是，当他推断，如果一个人群完全由安达曼-印度人（ASI）血统构成——即不包含任何亚姆纳亚人相关血统——那么他们的血统构成也必然包含相当数量的伊朗农民血统（其余部分则与小安达曼人相关）。

When Patterson inferred what would have been expected for a population of entirely ANI ancestry—one with no Andamanese-related ancestry—he determined that they would be a mixed population of Iranian farmer–related ancestry and steppe pastoralist–related ancestry. But when he inferred what would have been expected for a population of entirely ASI ancestry—one with no Yamnaya-related ancestry—he found that they too must have had substantial Iranian farmer–related ancestry (the rest being Little Andamanese–related).

这着实令人惊讶。我们发现，ANI 和 ASI 都含有大量伊朗血统，这意味着我们最初的假设——即印度人种谱系的两大主要祖先群体之一完全没有西欧亚血统——是错误的。事实上，伊朗农民的后裔曾两次对印度产生重大影响，并将他们的血统融入了 ANI 和 ASI 中。

This was a great surprise. Our finding that both the ANI and ASI had large amounts of Iranian-related ancestry meant that we had been wrong in our original presumption that one of the two major ancestral populations of the Indian Cline had no West Eurasian ancestry. Instead, people descended from Iranian farmers made a major impact on India twice, admixing both into the ANI and the ASI.

帕特森对我们关于印度深层历史的工作模型提出了一项重大修订。45^非洲印度人（ANI）的血统构成是混合的，其中约50%是草原祖先，与亚姆纳亚人有远亲关系；另外50%是来自草原民族的伊朗农民祖先。在向南扩张的过程中，他们遇到了其他族群。南亚土著居民（ASI）的血统也十分复杂，融合了早期从伊朗迁徙而来的农民后裔（约占其祖先的25%）和此前定居于南亚的狩猎采集者（约占其祖先的75%）。因此，南亚土著居民不太可能是此前定居于印度的狩猎采集者，而更有可能是将近东农业传播到南亚的人群。鉴于南亚土著居民的祖先与达罗毗荼语系语言高度相关，南亚土著居民的形成很可能也是达罗毗荼语系语言传播的过程。

Patterson proposed a major revision to our working model for deep Indian history.⁴⁵ The ANI were a mixture of about 50 percent steppe ancestry related distantly to the Yamnaya, and 50 percent Iranian farmer–related ancestry from the groups the steppe people encountered as they expanded south. The ASI were also mixed, a fusion of a population descended from earlier farmers expanding out of Iran (around 25 percent of their ancestry), and previously established local hunter-gatherers of South Asia (around 75 percent of their ancestry). So the ASI were not likely to have been the previously established hunter-gatherer population of India, and instead may have been the people responsible for spreading Near Eastern agriculture across South Asia. Based on the high correlation of ASI ancestry to Dravidian languages, it seems likely that the formation of the ASI was the process that spread Dravidian languages as well.

这些结果揭示了史前时期一个惊人相似的故事。欧亚大陆上两个面积相近的次大陆——欧洲和印度——都经历了类似的历史演变。大约九千年前，来自近东核心地区的农民迁徙至这两个地区——欧洲的农民来自安纳托利亚，印度的农民来自伊朗——他们带来了变革性的新技术，并与当地原有的狩猎采集人群通婚，在大约九千年至四千年间形成了新的混血群体。此后，这两个次大陆又受到了第二次大规模迁徙的影响，这次迁徙起源于草原地区。在这次迁徙中，讲印欧语系语言的亚姆纳亚牧民与沿途遇到的当地农民通婚，在欧洲形成了与……相关的民族。绳纹器文化，最终在印度形成了安达曼-尼罗河民族（ANI）。这些拥有草原和农民血统的人群随后与各自地区先前定居的农民融合，形成了我们今天在两个次大陆上看到的混血梯度。

These results reveal a remarkably parallel tale of the prehistories of two similarly sized subcontinents of Eurasia—Europe and India. In both regions, farmers migrating from the core region of the Near East after nine thousand years ago—in Europe from Anatolia, and in India from Iran—brought a transformative new technology, and interbred with the previously established hunter-gatherer populations to form new mixed groups between nine thousand and four thousand years ago. Both subcontinents were then also affected by a second later major migration with an origin in the steppe, in which Yamnaya pastoralists speaking an Indo-European language mixed with the previously established farming population they encountered along the way, in Europe forming the peoples associated with the Corded Ware culture, and in India eventually forming the ANI. These populations of mixed steppe and farmer ancestry then mixed with the previously established farmers of their respective regions, forming the gradients of mixture we see in both subcontinents today.

基因数据显示，亚姆纳亚人与印度和欧洲草原祖先的起源密切相关，因此他们显然是印欧语系传播到欧亚大陆这两个次大陆的先驱。值得注意的是，帕特森对印度人口历史的分析为此提供了另一条证据。他构建的印度渐变群模型基于两个祖先群体——印度-北印度人（ANI）和南印度人（ASI）——的简单混合。但当他更深入地研究并逐一检验印度渐变群的各个群体是否符合该模型时，他发现有六个群体并不符合该模型，因为它们的草原相关祖先与伊朗农民相关祖先的比例高于该模型的预期。这六个群体都属于婆罗门种姓——他们在社会中扮演着祭司和印欧语系梵语古代文献守护者的传统角色——尽管婆罗门在帕特森测试的群体中仅占约10%。对此的一种合理解释是，当ANI与ASI融合时，他们并非同质人群，而是包含着社会结构不同的亚群体，这些亚群体具有草原血统与伊朗相关血统的特定比例。那些守护印欧语系语言和文化的人拥有相对更多的草原血统，而由于种姓制度在世代传承血统和社会角色方面具有非凡的力量，即使经过数千年，ANI的古老底层结构仍然在当今的一些婆罗门身上得以体现。这一发现为草原假说提供了又一条证据，表明不仅印欧语系语言，而且印欧文化（体现在婆罗门祭司保存了数千年的宗教中）很可能是由祖先起源于草原的人们传播开来的。

The Yamnaya—who the genetic data show were closely related to the source of the steppe ancestry in both India and Europe—are obvious candidates for spreading Indo-European languages to both these subcontinents of Eurasia. Remarkably, Patterson’s analysis of population history in India provided an additional line of evidence for this. His model of the Indian Cline was based on the idea of a simple mixture of two ancestral populations, the ANI and ASI. But when he looked harder and tested each of the Indian Cline groups in turn for whether it fit this model, he found that there were six groups that did not fit in the sense of having a higher ratio of steppe-related to Iranian farmer–related ancestry than was expected from this model. All six of these groups are in the Brahmin varna—with a traditional role in society as priests and custodians of the ancient texts written in the Indo-European Sanskrit language—despite the fact that Brahmins made up only about 10 percent of the groups Patterson tested. A natural explanation for this was that the ANI were not a homogeneous population when they mixed with the ASI, but instead contained socially distinct subgroups with characteristic ratios of steppe to Iranian-related ancestry. The people who were custodians of Indo-European language and culture were the ones with relatively more steppe ancestry, and because of the extraordinary strength of the caste system in preserving ancestry and social roles over generations, the ancient substructure in the ANI is evident in some of today’s Brahmins even after thousands of years. This finding provides yet another line of evidence for the steppe hypothesis, showing that not just Indo-European languages, but also Indo-European culture as reflected in the religion preserved over thousands of years by Brahmin priests, was likely spread by peoples whose ancestors originated in the steppe.

由于缺乏南亚古代DNA样本，我们对印度人口迁徙的了解远不如对欧洲的了解那样清晰。一个悬而未决的谜团是印度河流域文明居民的祖先，他们分布在印度河流域各地。大约在四千五百年到三千八百年前，印度北部部分地区曾是人类迁徙的交汇点。我们至今尚未获得印度河流域文明居民的古代DNA，但包括我们团队在内的多个研究小组正致力于此。在2015年的一次实验室会议上，我们小组的分析师们就印度河流域文明居民可能的遗传祖先进行了猜测，结果众说纷纭。目前，仍有三种截然不同的可能性。第一种可能性是，印度河流域文明居民主要是该地区最早的伊朗裔农民的纯种后裔，他们使用早期达罗毗荼语。第二种可能性是，他们是南亚土著居民（ASI）——一个由伊朗裔农民和南亚狩猎采集者组成的混血群体——如果是这样，他们也可能使用达罗毗荼语。第三种可能性是，他们是古代印度人（ANI），其血统已融合了草原和伊朗农民的血统，因此很可能说的是印欧语系语言。这些假设意义截然不同，但借助古代DNA技术，印度历史上的这一谜团以及其他诸多谜团终将得到解答。

The picture of population movements in India is still far less crisp than our picture of Europe because of the lack of ancient DNA from South Asia. An outstanding mystery is the ancestry of the peoples of the Indus Valley Civilization, who were spread across the Indus Valley and parts of northern India between forty-five hundred to thirty-eight hundred years ago, and were at the crossroads of all these great ancient movements of people. We have yet to obtain ancient DNA from the people of the Indus Valley Civilization, but multiple research groups, including mine, are pursuing this as a goal. At a lab meeting in 2015, the analysts in our group went around the table placing bets on the likely genetic ancestry of the Indus Valley Civilization people, and the bets were wildly different. At the moment, three very different possibilities are still on the table. One is that Indus Valley Civilization people were largely unmixed descendants of the first Iranian-related farmers of the region, and spoke an early Dravidian language. A second possibility is that they were the ASI—already a mix of people related to Iranian farmers and South Asian hunter-gatherers—and if so they would also probably have spoken a Dravidian language. A third possibility is that they were the ANI, already mixed between steppe and Iranian farmer–related ancestry, and thus would instead likely have spoken an Indo-European language. These scenarios have very different implications, but with ancient DNA, this and other great mysteries of the Indian past will soon be resolved.

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寻找美洲原住民祖先

In Search of Native American Ancestors

起源故事

Origins Stories

在亚马逊苏鲁伊部落的起源传说中，神帕洛普先创造了他的兄弟帕洛普·莱雷古，然后创造了人类。帕洛普赐予美洲原住民部落吊床和饰品，并告诉他们纹身和穿孔，但他没有把这些东西赐予白人。帕洛普为每个族群创造了一种语言，并将这些族群散布到世界各地^。

In an origins story of the Suruí tribe of Amazonia, the god Palop first made his brother, Palop Leregu, and then created humans. Palop gave the Native American tribes hammocks and ornaments and told them to tattoo their bodies and pierce their lips, but he did not give any of these things to the whites. Palop created languages, one for each group, and scattered the groups across the earth.¹

这个起源故事是由一位致力于研究苏鲁伊文化的民族学家记录下来的。和世界各地的起源故事一样，学者们认为它是虚构的，之所以引人关注，是因为它揭示了一个社会的某些方面。但我们科学家也有自己的起源故事。我们喜欢认为这些故事更胜一筹，因为它们经过了科学方法的检验，并受到一系列证据的验证。但我们也应该保持谦逊。2012年，我领导了一项研究，声称从中美洲向南的所有美洲原住民——包括苏鲁伊人——都源自同一个族群，这个族群在大约一万五千年前迁徙到冰盖以南。^我当时对这个理论非常有信心，因为它与考古学的共识相符，所以我使用了“第一批美洲人”这个词来表明我们所强调的血统是一个创始血统。三年后，我发现我错了。苏鲁伊人和他们在亚马逊地区的一些邻居，他们的祖先来自另一个创始族群。美洲的居民，他们的祖先到达美洲的时间和路线，我们至今仍不甚了解^。3

This origins story was documented by an anthropologist working to understand Suruí culture, and, like origins stories the world over, it is viewed by scholars as fictional, of interest because of what it reveals about a society. But we scientists too have origins stories. We like to think these are superior because they are tested by the scientific method against a range of evidence. But some humility is in order. In 2012, I led a study that claimed that all Native Americans from Mesoamerica southward—including the Suruí—derived all of their ancestry from a single population, one that moved south of the ice sheets sometime after fifteen thousand years ago.² I was so confident of this theory, which fit with the consensus derived from archaeology, that I used the term “First American” to signal that the lineage we had highlighted was a founding lineage. Three years later, I found out I was wrong. The Suruí and some of their neighbors in Amazonia harbor some ancestry from a different founding population of the Americas, whose ancestors arrived at a time and along a route we still do not understand.³

如果说研究美洲人类历史的学者们有什么共识的话，那就是人类在新大陆的居住时间与人类在非洲和欧亚大陆的漫长历史相比，简直是沧海一粟。人类迟迟未能抵达美洲的原因在于将这片大陆与欧亚大陆分隔开来的地理屏障：西伯利亚广袤无垠的寒冷、严酷且贫瘠的土地，以及东西两侧的海洋。直到上一个冰河时期，拥有必要技能和技术的人类才抵达西伯利亚的东北角。在海平面足够低，以至于在如今的白令海峡地区出现了一座陆桥，使他们能够步行穿过这片区域到达阿拉斯加，并在那里生存了下来。到达阿拉斯加后，这些移民得以生存，但他们仍然无法向南迁徙，至少无法通过陆路，因为他们被一道由覆盖加拿大的数公里厚的冰盖连接而成的冰川冰墙阻挡了去路。

If there is anything that scholars studying the history of humans in the Americas agree on, it is that the span of human occupation of the New World has been the blink of an eye relative to the extraordinary length of the human occupation of Africa and Eurasia. The reason for humans’ late arrival to America lies in the geographical barriers that separate the continent from Eurasia: vast stretches of cold, harsh, and unproductive landscapes in Siberia, and oceans to the east and west. It took until the last ice age for Siberia’s northeastern corner to be visited by people with the skills and technology needed to survive there at a time when sea levels were low enough for a land bridge to emerge in what is now the Bering Strait region, enabling them to walk across to Alaska. Once there, the migrants were able to survive, but they still could not have traveled south, at least by land, as they were blocked by a wall of glacial ice formed by the joining together of kilometer-thick ice sheets that buried Canada.

美洲最初的居民是如何出现的？直到二十年前，主流假说是美洲伊甸园的大门大约在一万三千年前才开启。动植物遗骸的证据以及冰川地貌的放射性碳测年结果表明，到那时，冰盖已经融化到足以……冰层裂开，时间也足够长，使得原本光秃秃的岩石、淤泥和冰川融水逐渐被植被覆盖。^在科学叙事中，这条“无冰走廊”是美国版的以色列人穿越红海的陆路通道，正如圣经中以色列人出埃及记的故事一样。穿过这条通道的移民来到了北美大平原。在他们面前，是一片从未与人类猎人接触过的、充满巨型猎物的土地。不到一千年，人类就到达了南美洲南端的火地岛，尽情享用着漫游在这片土地上的野牛、猛犸象和乳齿象。

How were the Americas first peopled? Until two decades ago, the prevailing hypothesis was that the gates of the American Eden only opened after around thirteen thousand years ago. Evidence from plant and animal remains and the radiocarbon dating of glacial features indicate that by this time, the ice sheets had melted enough to allow a gap to open, and sufficient time had passed to allow the barren rocks, mud, and glacial runoff to give way to vegetation.⁴ In scientific storytelling, this “ice-free corridor” was an American version of the channel of dry land that the Israelites used to cross the Red Sea in the biblical account of the Exodus from Egypt. The migrants who passed through emerged into North America’s Great Plains. Before them was a land filled with massive game that had never before met human hunters. Within a thousand years, the humans had reached Tierra del Fuego at the foot of South America, feasting on the bison, mammoths, and mastodons that roamed the landscape.

人类最初从亚洲抵达美洲大陆的观点——这一观点至今仍是学者们的普遍共识——可以追溯到1590年耶稣会博物学家何塞·德·阿科斯塔。他认为古代人类不太可能横渡浩瀚的海洋，于是推测新大陆与旧大陆在当时尚未绘制地图的北极地区相连。 ⁵库克船长环球航行发现白令海峡狭窄后，这一观点更具说服力。20世纪20年代和30年代，考古学家在新墨西哥州的福尔松和克洛维斯遗址发现了文物和石器，其中包括混杂在已灭绝猛犸象骨骼中的矛尖，这些发现为人类在美洲温带地区的存在提供了确凿的证据。此后，在北美数百个遗址中都发现了克洛维斯式矛尖，有时甚至嵌在野牛和猛犸象的骨骼中。在广阔的范围内，他们的风格却十分相似——这与后来的文化在石器制造风格上的地域差异形成鲜明对比——这符合快速扩张的预期（因为人们正迁徙到人类的真空地带）。现有证据表明，克洛维斯文化出现在考古记录中的时间大约与地质学上证实的无冰走廊的开启时间相吻合，一切似乎都吻合。因此，人们自然而然地认为，克洛维斯文化的实践者是冰盖以南的第一批人类，也是今天所有美洲原住民的祖先。

The notion that humans first reached an empty America from Asia—an idea that today is still the overwhelming consensus among scholars—dates back to the Jesuit naturalist José de Acosta in 1590, who, finding it unlikely that ancient peoples could have navigated across a great ocean, conjectured that the New World was joined to the Old in the then-unmapped Arctic.⁵ This idea gained plausibility when the narrowness of the Bering Strait was discovered by the circumnavigation of Captain Cook. Scientific evidence for humans in temperate America at the tail end of the last ice age came in the 1920s and 1930s, when archaeologists working at the sites of Folsom and Clovis, New Mexico, discovered artifacts and stone tools—including spear tips mixed in among the bones of extinct mammoths—that were effectively smoking guns proving a human presence. Clovis-style spear tips have since been found over hundreds of sites across North America, sometimes embedded in bison and mammoth skeletons. Their similar style over vast distances—contrasting with the regional variation in stone toolmaking styles of the cultures that followed—is what one might expect for an expansion that occurred fast (as the people were moving into a human vacuum). The available evidence suggests that the Clovis culture appeared in the archaeological record around the time of the geologically attested opening of the ice-free corridor, so everything seemed to fit. It seemed natural to think that people practicing the Clovis culture were the first humans south of the ice sheets, and were also the ancestors of all of today’s Native Americans.

这种“克洛维斯优先”模式认为，克洛维斯文化的创造者从无冰走廊出现，并逐渐向人类传播。空旷的大陆成为美洲史前史的标准模型。它加剧了考古学家对克洛维斯文化之前遗址的质疑。 ⁶它影响了语言学家，他们声称发现了大量不同的美洲原住民语言的共同起源。 ⁷ 当时可用的线粒体DNA数据也与当今绝大多数美洲原住民的祖先源自单一来源的辐射演化相一致，尽管仅凭这些数据无法确定这种辐射演化发生在克洛维斯文化时期还是更早。 ⁸

This “Clovis First” model, in which the makers of the Clovis culture emerged from the ice-free corridor and proceeded to people an empty continent, became the standard model of American prehistory. It fostered skepticism among archaeologists regarding claims of pre-Clovis sites.⁶ It influenced linguists who claimed to find a common origin for a large number of diverse Native American languages.⁷ The mitochondrial DNA data available at the time was also consistent with the great majority of the ancestry of present-day Native Americans deriving from a radiation from a single source, although with such data alone it was not possible to determine whether that radiation occurred at the time of Clovis or before.⁸

1997年，克洛维斯人是美洲第一批居民的观点遭受重创。那一年，智利蒙特维德遗址的考古发掘成果公布，该遗址出土了被屠宰的乳齿象骨骼、木质建筑残骸、打结的绳索、古代火塘以及与北美克洛维斯遗迹风格迥异的石器。9 蒙特维德遗址^的放射性碳测年结果表明，部分文物可追溯至约14000年前，远早于北部数千公里处无冰走廊的形成。一群此前曾驳斥过许多克洛维斯文化之前存在人类的说法的持怀疑态度的考古学家，也在同年考察了该遗址。尽管他们出发前对遗址的年代持怀疑态度，但离开时却确信无疑。他们对蒙特维德遗址的结论的接受，也促使人们接受了其他地区的考古发现，这些发现同样指向无冰走廊形成之前以及克洛维斯文化之前美洲已有人类存在。在美国西北部俄勒冈州的佩斯利洞穴，也发现了几乎同样有力的证据，证明冰川消融前人类曾在此居住。那里未受扰动的土壤层中发现的古代粪便，其年代可追溯到大约一万四千年前，并且从中提取出了人类线粒体DNA序列。 ¹⁰

A major blow to the idea that Clovis groups were the first Americans came in 1997. That year marked the publication of the results of excavations at the site of Monte Verde in Chile, which contains butchered mastodon bones, wooden remains of structures, knotted string, ancient hearths, and stone tools with no stylistic similarities to the Clovis remains from North America.⁹ The radiocarbon dates of Monte Verde indicated that some of the artifacts there dated to around fourteen thousand years ago, definitively before the ice-free corridor had opened thousands of kilometers to the north. A group of skeptical archaeologists who had previously shot down many pre-Clovis claims visited the site that same year, and though they arrived doubting that the site could be that old, they left convinced. Their acceptance of Monte Verde was followed by the acceptance of finds elsewhere that also pointed to a pre-ice-free corridor and a pre-Clovis human presence in the Americas. Nearly as strong a case for a pre-ice-free corridor occupation has been made at the Paisley Caves in Oregon in the northwestern United States, where ancient feces in undisturbed soil layers have also been dated to around fourteen thousand years ago, and have yielded human mitochondrial DNA sequences.¹⁰

在无冰走廊开放之前，人类是如何到达冰盖以南的呢？冰河时代鼎盛时期，冰川直接延伸入海，在加拿大西海岸形成了一道长达一千多公里的屏障。但在20世纪90年代，地质学家和考古学家通过重建冰川消退的时间，发现早在16000年前，部分海岸线就已经没有冰雪覆盖。由于海平面上升，目前尚未发现这一时期沿海地区的考古遗址。自冰河时代以来，海岸线向南延伸了不到一百米，淹没了所有可能曾经沿岸分布的考古遗址。因此，这一时期沿海地区缺乏人类居住的考古证据，并不能证明过去这里从未有人居住过。如果沿海路线假说成立，那么当时或之后（但仍有时间到达蒙特维德），人类可能沿着无冰的海岸线步行，或许会借助船只或木筏绕过冰封的路段，并在内陆无冰通道开放的数千年前就抵达冰盖以南。

How could humans have gotten south of the ice sheets before the ice-free corridor was open? During the peak of the ice age, glaciers projected right into the sea, creating a barrier more than a thousand kilometers in length along the western seaboard of Canada. But in the 1990s, geologists and archaeologists, reconstructing the timing of the ice retreat, realized that portions of the coast were ice-free after sixteen thousand years ago. There are no known archaeological sites along the coast from this period, as sea levels have risen more than a hundred meters since the ice age, submerging any archaeological sites that might have once hugged the shoreline. The absence of archaeological evidence for human occupation along the coast in this period is therefore not evidence that there was no such occupation in the past. If the coastal route hypothesis is right, humans could have walked at that time or later (but still in time to reach Monte Verde) along ice-free stretches of the coastline, possibly bypassing ice-covered sections with boats or rafts, and arriving south of the ice millennia before the interior ice-free corridor opened.

古代DNA研究如今也清楚地表明了“克洛维斯第一”观点的谬误之处——它忽略了美洲原住民人口历史中一个重要的分支。2014年，埃斯克·威勒斯列夫及其同事发表了蒙大拿州出土的一具婴儿遗骸的全基因组数据。该婴儿的考古背景表明他属于克洛维斯文化，其放射性碳测年结果显示其年代距今约13000年。 ¹¹他们的分析表明，这名婴儿的确与许多美洲原住民拥有相同的祖先群体，但他的基因数据也显示，在他生活的年代，美洲原住民群体之间已经出现了深刻的分化。这名克洛维斯婴儿的遗骸位于分化的一侧：这一侧为当今中美洲和南美洲所有美洲原住民群体贡献了绝大部分的祖先。分化的另一侧则包括如今生活在加拿大东部和中部的美洲原住民。这种情况发生的唯一解释是，在克洛维斯文化之前存在一个群体，该群体孕育了主要的美洲原住民血统。

Ancient DNA studies have also now made it clear just how wrong the Clovis First idea is—how it misses a whole deep branch of Native American population history. In 2014, Eske Willerslev and his colleagues published whole-genome data from the remains of an infant excavated in Montana whose archaeological context assigned him to the Clovis culture and whose radiocarbon age was a bit after thirteen thousand years ago.¹¹ Their analysis showed that this infant was definitely from the same ancestral population as many Native Americans, but his genetic data also showed that by the time he lived, a deep split among Native American populations had already developed. The remains from the Clovis infant were on one side of that split: the side that contributed the lion’s share of ancestry to all Native American populations in Mesoamerica and South America today. The other side of the split includes Native American peoples who today live in eastern and central Canada. The only way this could have happened is if there had been a population that lived before Clovis and that gave rise to major Native American lineages.

对西方科学的不信任

Mistrust of Western Science

像克洛维斯婴儿这样的古代DNA研究有可能解决有关美洲原住民人口历史的争议。但这类研究对这些人群的当代后裔的影响并非完全积极。这是因为在过去的五百年里，我们屡次目睹欧洲血统的人利用西方科学工具剥削美洲原住民的案例。这导致一些美洲原住民群体与学术界之间产生了不信任——这种不信任使得开展基因研究变得困难重重。

Ancient DNA studies such as the one of the Clovis infant have the potential to resolve controversies about Native American population history. But such studies have resonances for present-day descendants of those populations that are not entirely positive. That is because the last five hundred years have witnessed repeated cases in which people of European ancestry have exploited the indigenous peoples of the Americas using the toolkit of Western science. This has engendered distrust between some Native American groups and the scholarly community—a distrust that makes carrying out genetic studies challenging.

1492年欧洲人抵达美洲后，美洲原住民的人口和文化在欧洲疾病、军事征服以及旨在掠夺美洲大陆财富并强迫其居民皈依基督教的经济和政治体制的重压下迅速衰落。历史是由胜利者书写的，而欧洲征服后对美洲历史的改写尤为彻底，因为在欧洲人到来之前，除中美洲以外，美洲其他地方都没有文字。在墨西哥，西班牙人焚烧了原住民的书籍，因此大多数美洲原住民的文字都付之一炬。口头传统也遭受了重创。语言的改变、宗教的皈依以及对原住民习俗的歧视，使得美洲原住民文化的地位远低于欧洲文化。

After the arrival of Europeans in the Americas in 1492, Native American populations and cultures collapsed under the pressure of European diseases, military campaigns, and an economic and political regime set on exploiting the riches of the continent and converting its inhabitants to Christianity. History is written by the victors, and the rewriting of the past after the European conquests has been particularly complete in the Americas, as there was no written language except in Mesoamerica prior to the arrival of Europeans. In Mexico, the Spanish burned indigenous books, and so most Native American writing literally went up in flames. The oral traditions suffered too. Language change, religious conversion, and discrimination against indigenous ways led Native American culture to be relegated to a lower status than European culture.

现代基因组学为追溯历史提供了一种意想不到的途径。非裔美国人——另一个历史被窃取的群体，他们的祖先是被从非洲掳掠而来的奴隶——正走在利用遗传学追溯根源的前沿。然而，尽管美洲原住民个体常常对他们的基因历史表现出浓厚的兴趣，但部落委员会有时却持敌对态度。一种普遍的担忧是，对美洲原住民历史的基因研究是欧洲人试图“启蒙”他们的又一例证。过去类似的尝试——例如通过皈依基督教或接受西方文化教育——最终导致了美洲原住民文化的瓦解。此外，人们也意识到，一些科学家研究美洲原住民是为了了解主要由非美洲原住民感兴趣的问题，而忽视了美洲原住民自身的利益。

Modern genomics offers an unexpected way to recover the past. African Americans—another population that has had its history stolen as its ancestors descend from people kidnapped into slavery from Africa—are at the forefront of trying to use genetics to trace roots. But if individual Native Americans often express a great interest in their genetic history, tribal councils have sometimes been hostile. A common concern is that genetic studies of Native American history are yet another example of Europeans trying to “enlighten” them. Past attempts to do so—for example, by conversion to Christianity or education in Western culture—have led to the dissolution of Native American culture. There is also an awareness that some scientists have studied Native Americans to learn about questions of interest primarily to non–Native Americans, without paying attention to the interests of Native Americans themselves.

最早对美洲原住民基因研究做出强烈反应的群体之一来自亚马逊地区的卡里蒂亚纳人。1996年，医生采集了卡里蒂亚纳人的血液样本，并承诺改善他们的医疗保健服务，但这些承诺从未兑现。卡里蒂亚纳人对此深感痛心，他们带头反对将他们的样本纳入一项旨在研究人类遗传多样性的国际研究——人类基因组多样性计划，并最终阻止了该计划获得资助。值得注意的是，在后续分析美洲原住民与其他族群亲缘关系的研究中，卡里蒂亚纳人的DNA样本的使用频率高于其他任何单一美洲原住民群体。被广泛研究的卡里蒂亚纳人DNA样本并非来自1996年那组备受争议的样本，而是来自1987年进行的一次样本采集。当时，参与者被告知研究目的，并被告知他们的参与完全出于自愿。^然而，卡里蒂亚纳人后来遭受的剥削经历，给该群体的DNA研究蒙上了一层阴影。

One of the first strong responses to genetic studies of Native Americans came from the Karitiana of Amazonia. In 1996, physicians collected blood from the Karitiana, promising participants improved access to health care, which never came. Distressed by this experience, the Karitiana were at the forefront of objections to the inclusion of their samples in an international study of human genetic diversity—the Human Genome Diversity Project—and were instrumental in preventing that entire project from being funded. Ironically, DNA samples from the Karitiana have been used more than those of any other single Native American population in subsequent studies that have analyzed how Native Americans are related to other groups. The Karitiana DNA samples that have been widely studied are not from the disputed set from 1996. Instead, they are from a collection carried out in 1987 in which participants were informed about the goals of the study and told that their involvement was voluntary.¹² However, the Karitiana people’s later experience of exploitation has put a cloud over DNA studies in this population.

另一个强烈反对针对美洲原住民进行基因研究的例子来自居住在美国西南部峡谷地带的哈瓦苏派人。1989年，亚利桑那州立大学的研究人员采集了哈瓦苏派人的血液样本，试图了解该部落罹患2型糖尿病的高风险。参与者签署了书面同意书，同意参与一项“行为/医学疾病病因研究”。然而，同意书的措辞赋予了研究人员很大的自由裁量权，使其可以对同意的含义做出非常宽泛的解释。之后，研究人员将这些样本分享给了许多其他科学家，他们利用这些样本研究了从精神分裂症到哈瓦苏派史前史等各种课题。哈瓦苏派的代表认为，这些样本的用途与他们成员最初同意的目的截然不同——也就是说，即使同意书的细则另有规定，但在采集样本时，他们清楚地知道这项研究的重点应该是糖尿病。这场纠纷最终导致诉讼、样品归还以及大学同意支付70万美元赔偿金^。13

Another strong response to genetic research on Native Americans came from the Havasupai, who live in the canyonlands of the U.S. Southwest. Blood from the Havasupai was sampled in 1989 by researchers at Arizona State University who were trying to understand the tribe’s high risk for type 2 diabetes. The participants gave written consent to participate in a “study [of] the causes of behavioral/medical disorders,” and the language of the consent forms gave the researchers latitude to take a very broad view of what the consent meant. The researchers then shared the samples with many other scientists who used them to study topics ranging from schizophrenia to the Havasupai’s prehistory. Representatives of the Havasupai argued that the samples were being used for a purpose different from the one to which its members understood they had agreed—that is, even if the fine print of the forms said one thing, it was clear to them when the samples were collected that the study was supposed to focus on diabetes. This dispute led to a lawsuit, the return of the samples, and an agreement by the university to pay $700,000 in compensation.¹³

对基因研究的敌意甚至写入了部落法律。2002年，纳瓦霍族——与许多其他美洲原住民部落一样，根据条约在政治上部分独立于美国——通过了一项基因研究禁令，禁止纳瓦霍族成员参与任何基因研究，无论是疾病风险因素研究还是人口历史研究。纳瓦霍族编写的一份文件概述了这项禁令的内容，其中列出了大学研究人员在考虑研究项目时应注意的要点。该文件写道：“部落严禁进行人类基因组检测。纳瓦霍人是由‘变身女神’创造的；因此他们知道自己的起源。” ¹⁴

The hostility to genetic research has even entered into tribal law. In 2002, the Navajo—who along with many other Native American tribes are by treaty partly politically independent of the United States—passed a Moratorium on Genetic Research, forbidding participation of Navajo tribal members in genetic studies, whether of disease risk factors or population history. A summary of this moratorium can be found in a document prepared by the Navajo Nation, outlining points for university researchers to take into account when considering a research project. The document reads: “Human genome testing is strictly prohibited by the Tribe. Navajos were created by Changing Woman; therefore they know where they came from.”¹⁴

2012年，我正处于撰写一篇关于不同美洲原住民群体遗传变异的论文的最后阶段时，了解到纳瓦霍族暂停研究的禁令。在收到论文的好评后，我要求每位提供样本的研究人员再次确认，与样本相关的知情同意书是否符合人口历史研究的标准，并确认他们本人是否支持将样本纳入我们的研究。这导致包括纳瓦霍族在内的三个群体退出了研究。这三个群体都来自美国，反映出美国遗传学研究人员对美洲原住民遗传学研究的担忧。2013年，我参加了一个关于美洲原住民遗传学研究的研讨会，会上多位研究人员站起来表示，卡里蒂亚纳人、哈瓦苏派人、纳瓦霍人和其他一些群体的反应让他们对开展任何关于美洲原住民的研究（包括疾病研究）都过于谨慎。

I became aware of the Navajo moratorium in 2012, while I was in the final stages of preparing a manuscript on genetic variation among diverse Native Americans. After receiving favorable reviews of our manuscript, I asked each researcher who contributed samples to double-check whether the informed consent associated with the samples was consistent with studies of population history and to confirm that they themselves stood behind the inclusion of their samples in our study. This led to withdrawal of three populations from the study, including the Navajo. All three populations were from the United States, reflecting the anxiety that has seized U.S. genetic researchers about genetic studies of Native Americans. At a workshop on genetic studies of Native Americans that I attended in 2013, multiple researchers stood up from the audience to say that the responses of the Karitiana, Havasupai, Navajo, and others had made them too wary to do any research on Native Americans (including disease research).

对研究美洲原住民群体遗传变异感兴趣的科学家们对这种情况感到沮丧。我理解欧洲人和非洲人来到美洲给美洲原住民群体带来的毁灭性影响，这种影响在我和我的同事分析的数据中也随处可见。但我并不了解任何分子生物学研究（包括遗传学——这个几乎完全是在二战结束后才兴起的领域）对历史上遭受迫害的群体造成重大伤害的案例。当然，生物材料的使用方式可能并未得到其来源群体的认可，这并非仅限于美洲原住民，而是有据可查的案例。例如，来自巴尔的摩的非裔美国女性亨丽埃塔·拉克斯的宫颈癌肿瘤细胞在她去世后，未经她本人及其家人同意，就被分发到世界各地数千个实验室，成为癌症研究的重要基础。¹⁵但总的来说，有理由认为，现代DNA变异研究——不仅针对美洲原住民，也针对包括南部非洲桑人、犹太人、欧洲罗姆人以及南亚部落或种姓群体在内的许多其他群体——是一种积极的力量，有助于我们理解和治疗这些群体。了解这些人群中的疾病情况，并打破那些被用来为歧视辩护的根深蒂固的种族观念。我怀疑，一些美洲原住民之间出现的这种不信任感，最终是否会对他们造成实质性的伤害。作为一名遗传学家，我是否有责任做得更多，而不仅仅是尊重那些不愿参与基因研究的人的意愿，而是应该以尊重而有力的方式，论证此类研究的价值。

Scientists interested in studying genetic variation in Native American populations feel frustrated with this situation. I understand something of the devastation that the coming of Europeans and Africans to the Americas wrought on Native American populations, and its effects are also evident everywhere in the data I and my colleagues analyze. But I am not aware of any cases in which research in molecular biology including genetics—a field that has arisen almost entirely since the end of the Second World War—has caused major harm to historically persecuted groups. Of course, there have been well-documented cases of the use of biological material in ways that may not have been appreciated by the people from whom it was taken, not just in Native Americans. For example, the cervical cancer tumor cells of Henrietta Lacks, an African American woman from Baltimore, were distributed after her death, without her consent and without the knowledge of her family, to thousands of laboratories around the world, where they have become a mainstay of cancer research.¹⁵ But overall there is an argument to be made that modern studies of DNA variation—not just in Native Americans, but also in many other groups including the San of southern Africa, Jews, the Roma of Europe, and tribal or caste groups from South Asia—are a force for good, contributing to the understanding and treatment of disease in these populations, and breaking down fixed ideas of race that have been used to justify discrimination. I wonder if the distrust that has emerged among some Native Americans might be, in the balance, doing Native Americans substantial harm. I wonder whether as a geneticist I have a responsibility to do more than just respect the wishes of those who do not wish to participate in genetic research, but instead should make a respectful but strong case for the value of such research.

纳瓦霍族样本被撤回令我们感到非常痛心，因为这些样本的知情同意记录最为完善。与我们分享这些样本的研究人员于1993年亲自采集了这些样本，当时他在纳瓦霍族保留地的迪内学院组织了一次“DNA日”活动，因此样本的交接过程清晰明确。在研讨会上，他询问参与者是否愿意捐献样本，用于广泛的人口历史研究——特别是那些“强调世界各民族密切相关，并强调人类起源统一性”的研究——而愿意参与的纳瓦霍族成员签署了同意书。然而，九年后，部落委员会的禁令推翻了这些个人参与研究的决定。

The withdrawal of Navajo samples from our study was distressing, since they were among those with the very best documentation of informed consent. The researcher who shared the samples with us had collected them personally in 1993 as part of a “DNA day” that he had organized at Diné College on Navajo lands, so there was no ambiguity involved in the handoff of samples along a human chain. During the workshop, he asked participants if they wished to donate their samples for the explicit purpose of broad studies of population history—specifically for studies that “give prominence to the idea that all peoples of the world are closely related and emphasize the unity of human origins”—and members of the Navajo tribe who wished to participate signed a form indicating that they did. Yet these individuals’ personal decisions to participate in the study were overruled by the tribal council’s moratorium nine years later.

我们是否应该尊重捐献样本的大学生的意愿，还是尊重部落委员会后来的决定？在这个案例中，我们回避了这个问题，同意了那位研究人员的要求，他非常担心，要求我们不要将这些样本纳入研究。我始终对这个决定感到不安。我认为，纳入这些样本才是对那些选择捐献DNA用于历史研究的个人的意愿的最佳尊重。但我承认，不同的文化有不同的视角。一些美洲原住民伦理学家和社区领袖正在发起一场运动，认为任何以部落为研究对象的研究，只有在进行社区咨询（而不仅仅是获得个人知情同意）的情况下才应被视为可接受。 ¹⁶这些担忧促使一些关于人类遗传变异的国际研究在纳入样本之前，除了获得个人知情同意外，还进行了社区咨询。 ¹⁷极少数研究人员研究现在，几乎所有关于美洲原住民遗传多样性的研究都会咨询部落当局，以获得对研究设计的反馈——有时还会获得明确的社区同意——即使这样做在法律上并没有要求。

Should we have respected the wishes of the college students who donated the samples, or the later decision of the tribal council? In the instance, we avoided the issue, acceding to the request of the researcher, who was so concerned that he asked us not to include the samples in the study. I was never comfortable with this decision. I felt that including the samples would best respect the wishes of the individuals who chose to donate their DNA for studies of their history. But I recognize that different cultures have different perspectives. There is a movement among some Native American ethicists and community leaders to argue that any research that has as its subject a tribe should only be considered acceptable if there is community consultation, not just informed individual consent.¹⁶ These concerns prompted some international studies of human genetic variation to carry out community consultation in addition to individual informed consent before including samples.¹⁷ The very few researchers studying Native American genetic diversity almost all now consult with tribal authorities to obtain feedback on study design—and sometimes to obtain explicit community consent—even if doing so is not legally required.

这里存在一个关于基因研究伦理责任的普遍性问题。当我研究一个人的基因组时，我不仅了解该个体的基因组，也了解其家族和祖先的基因组。我还了解了社群中的其他成员——这些祖先的其他后代。我在这里的责任是什么？我不仅对研究对象的近亲负有责任，而且对他们家族中其他更远亲属、他们的族群以及我们整个人类也负有责任。如果采取极端立场，认为需要咨询所有人，那么人类遗传学（包括基因医学）的科学进步将几乎不可能实现。像我这样的小型实验室的科学家根本没有足够的时间与每个可能对这项研究感兴趣的部落群体进行交流。

There is a general issue here about the ethical responsibilities of genetic research. When I examine an individual’s genome, I learn not only about the genome of the individual, but also about those of his or her family, and ancestors. I also learn about other members of the community—other descendants of those same ancestors. What are my responsibilities here? What do I owe not only to close relatives of the individual I study, but also to other more distantly related members of their family, to their population, and to our species as a whole? An extreme position that everyone needs to be consulted would make scientific progress in human genetics (including genetic medicine) nearly impossible. There would not be enough time for scientists in modest-sized laboratories like mine to talk with every tribal group that might be interested in the work.

我个人认为，作为科学界，我们需要找到一个折衷方案，一种无需获得所有相关团体或部落许可的方法。另一方面，考虑到北美部落社区的担忧不无道理——这些担忧源于他们长期遭受剥削的历史——我们科学家在研究美洲原住民人口历史时，应该努力开展有意义的宣传工作，以确保我们撰写的任何论文都能充分考虑原住民的视角。如何进行此类磋商的具体细节需要进一步商讨，而且在我看来，永远不会有让所有人都满意的解决方案。但我们需要努力改善目前面临的困境：许多研究人员由于害怕受到批评，以及考虑到完成一些部落代表和学者建议的所有磋商工作需要投入大量时间，而不愿开展任何关于美洲原住民遗传变异的研究。这种情况导致对美洲原住民遗传变异的研究陷入停滞——除了那些对科学研究抱有敌意的人之外，没有人希望看到这一领域的研究进展。

My own perspective is that we need as a scientific community to arrive at a middle ground, an approach that does not require obtaining permission from every possible interested group or tribe. On the other hand, given the well-founded concerns of tribal communities in North America, which have developed as a result of a persistent history of exploitation, we scientists should aspire to carry out meaningful outreach when we study Native American population history to ensure that any manuscripts we write are sensitive to indigenous perspectives. The details of how to achieve such consultation need to be worked out, and it seems to me that there will never be a solution that everyone will find comfortable. But we need to try to make progress beyond the situation we are facing right now, in which many researchers are reluctant to undertake any studies of Native American genetic variation for fear of criticism, and because of the extraordinary time commitment that would be required in order to accomplish all the consultations that some tribal representatives and scholars have recommended. This has had the effect of putting research into genetic variation among Native Americans into a deep chill—with far less research in this area going on than anyone but the people most hostile to scientific research would like.

关于骨头的争议

Disputes over Bones

对人口历史进行古代DNA研究通常不像对现代人群的研究那样充满争议。然而，1990年，美国国会通过了《美国原住民墓葬保护与归还法案》（NAGPRA），该法案要求接受美国政府资助的机构联系美洲原住民部落，并主动提出归还文化文物，包括来自美洲原住民能够证明与其存在生物学或文化联系的群体的骨骼。这意味着美洲原住民遗骸正被归还给美洲原住民部落，而对许多样本进行古代DNA分析的机会也随之消失。NAGPRA对近一千年内的考古遗骸影响最大，因为这些遗骸与现存的美洲原住民部落之间存在文化联系的证据相对较强。但对于年代非常久远的遗骸，例如1996年在美国华盛顿州土地上发现的约8500年前的肯纳威克人，文化联系的证据则难以成立。

Ancient DNA studies of population history are mostly not as fraught as studies of present-day people. However, in 1990, the U.S. Congress passed the Native American Graves Protection and Repatriation Act (NAGPRA), which requires institutions that receive U.S. funding to contact Native American tribes and offer to return cultural artifacts, including bones that are from groups to which Native Americans can prove a biological or cultural connection. This has meant that Native American remains are being returned to Native American tribes and the opportunity to carry out ancient DNA analysis on many of the samples is disappearing. NAGPRA has had its greatest impact on archaeological remains dating to within the last thousand years, for which a relatively strong case can be made for cultural connections with living Native American tribes. The case for cultural connection is harder to make for very old remains, such as the approximately eighty-five-hundred-year-old Kennewick Man found on U.S. lands in Washington State in 1996.

肯纳威克人的骨骼最初计划归还给五个声称他是其祖先的美洲原住民部落，但由于法院裁定没有充分的科学证据证明他是美洲原住民，并依据《美国原住民坟墓保护和归还法》（NAGPRA）的规定，最终决定将其用于科学研究。为了赢得诉讼，挑战部落主张的科学家们援引了骨骼形态学分析，指出肯纳威克人的骨骼更接近环太平洋地区的亚洲人和太平洋岛民，而非现代美洲原住民。 ¹⁸ 然而，2015年，埃斯克·威勒斯列夫及其同事提取并研究了肯纳威克人的古代DNA，结果表明这些形态学研究的结论是错误的。 ¹⁹事实上，肯纳威克人与其他大多数美洲原住民一样，都源自同一个广泛的祖先群体。

Kennewick Man’s skeleton was initially slated for return to five Native American tribes that claimed him as an ancestor, but was made available for scientific study instead after courts found that there was no good scientific evidence that he was Native American under the rules of NAGPRA. To win their case, the scientists who challenged the tribal claims pointed to analyses of skeletal morphology that suggested that his skeleton was closer to Pacific Rim Asian and Pacific islander populations than to present-day Native Americans.¹⁸ In 2015, though, Eske Willerslev and his colleagues extracted and studied ancient DNA from Kennewick Man, which showed that these conclusions from the morphological studies were wrong.¹⁹ Kennewick Man is in fact derived from the same broad ancestral population as most other Native Americans.

只要能够比较两种类型的数据，古DNA分析就优于形态学分析。原因很简单。骨骼形态学研究只能检测少数个体间存在差异的特征，因此通常只能支持不确定的群体归属。相比之下，基因分析数万个独立位点使得精确的群体归属成为可能。因此，仅基于少量形态特征来描述单个样本（例如肯纳威克人）的祖源，无法令人信服地区分美洲原住民和环太平洋地区的祖源。而基因数据则可以做到这一点。

Ancient DNA trumps morphological analysis whenever it is possible to compare the two types of data. The reason is simple. Morphological studies of skeletons can only examine a handful of traits that are variable among individuals, and thus can usually support only uncertain population assignment. In contrast, genetic analyses of tens of thousands of independent positions allow exact population assignment. Thus, the characterization of the ancestry of a single sample (like Kennewick Man) based on a small number of morphological traits cannot convincingly distinguish between Native American and Pacific Rim ancestry. Genetic data can.

虽然古代DNA研究明确证实了肯纳威克人的美洲原住民血统，但他与声称拥有其遗骸的华盛顿州美洲原住民群体之间是否存在特别密切的联系却并不明朗。发表肯纳威克人基因组的论文采集了科尔维尔部落的DNA样本，该部落是声称与肯纳威克人有亲缘关系的五个部落之一，论文认为数据与直接联系相符。然而，科尔维尔部落是科学家分析的美国本土48个州中唯一的部落，仔细审视论文的细节后，并没有令人信服的证据表明肯纳威克人与科尔维尔部落的亲缘关系比与远在南美洲的美洲原住民的亲缘关系更近。^此外，科尔维尔部落的数据也无法向科学界进行独立分析——尽管发表该数据的期刊要求共享数据作为发表的必要条件，但我的团队在提出请求后仍未获得这些数据。

While the ancient DNA study produced clear proof of the Native American ancestry of Kennewick Man, it was not so clear whether he bears a particularly strong relationship to the Washington State Native American populations that made claims on his remains. The paper reporting the Kennewick Man genome sampled DNA from the Colville tribe, one of the five tribes staking a claim of relationship to him, and argued that the data were consistent with a direct link. However, the Colville was the only tribe from the lower forty-eight states of the United States that the scientists analyzed, and a close look at the details of the paper provides no compelling case that Kennewick Man is more closely related to the Colville tribe than he is to Native Americans as far away as South America.²⁰ The Colville data are also not available to the scientific community for independent analysis—they were not provided to my group on request despite the fact that the journal in which they were published requires sharing of data as a condition for publication.

对基因数据的主观解读并非肯纳威克人独有。2017年，一项对一具约10300年前的骨骼的研究声称，这具骨骼出土于今加拿大太平洋沿岸的一个岛屿上，并以此证明该地区自肯纳威克人时代起，一直延续至今的美洲原住民血统。 ²¹但对该论文中分析结果的审查表明，这具骨骼与当地居民的亲缘关系并不比与南美洲原住民的亲缘关系更近。

Wishful interpretation of genetic data is not limited to Kennewick Man. In 2017, a study of an approximately 10,300-year-old skeleton excavated from an island off the Pacific coast of present-day Canada, claimed evidence for an unbroken presence of a lineage of Native Americans in the same region from his time until to the present day.²¹ But an examination of the analyses presented in the paper showed that this individual, too, was no more closely related to local people than to Native Americans in South America.

以上仅是两个例子，说明古代DNA文献中充斥着未经证实的、声称古代骨骼与现代人群之间存在直接祖先联系的说法，而这个问题并非美洲独有。与原住民合作的科学家有动机提出此类说法，因为当地群体往往欢迎这类说法，并能借此获得样本。正常的科学程序——即科学家指出缺乏数据有力支持的说法——也未能发挥应有的作用。令人担忧的是，当群体成员直接……人们在进行自身历史的科学研究时，往往会受到某些事实真实性的制约，从而影响研究结果的呈现。而那些没有参与研究的科学家，又常常因为担心后果而不敢指出问题所在。

These are just two examples of how the ancient DNA literature is beginning to fill up with unsubstantiated claims of direct ancestral links between ancient skeletons and groups living today, a problem that is not limited to the Americas. Scientists working with indigenous people have an incentive to make such claims, as claims like this are often welcomed by local groups, and open the door to sampling. The normal scientific process, in which scientists point out claims that are not compellingly supported by data, is also not working as it should. A concern is that when members of groups are directly engaged in scientific investigation of their own history, people’s wish that certain things should be true often colors presentation of the findings. And scientists not involved in the work are often too anxious about repercussions to point out problems.

肯纳威克人案充满争议，最终诉诸法庭，导致学术界与美洲原住民部落之间产生敌对情绪。该案对研究美洲原住民人口历史的科学家造成了影响，并使相关研究变得更加困难。根据我与专注于美洲原住民史前史的考古学家、人类学家和博物馆馆长的交流经验，我清楚地感受到，许多人对归还具有重要科学价值的骨骼藏品深感痛惜，他们希望将这些藏品继续留在博物馆，同时也承认，在美国征用美洲原住民土地的过程中，许多藏品的收集方式存在诸多疑点。 ²²与之形成鲜明对比的是，许多美洲原住民也对祖先遗骸遭到扰乱感到痛心。为了平衡各方利益和法律规定，许多博物馆都聘请了“NAGPRA官员”，他们的职责是识别与特定美洲原住民部落相关的文化和骨骼遗骸，并与这些部落的代表联系，以归还这些物品。但我接触过的NAGPRA官员虽然都致力于严格遵守法律条文，并且工作专业，但他们也谨慎行事，避免越权。当像肯纳威克人那样，遗骸被归还给部落却没有NAGPRA法规要求的生物学或文化联系证据时，他们感到非常痛心。

The Kennewick Man case was contentious and played itself out in court, engendering hostility between academics and Native American tribes. It has had consequences for scientists interested in Native American population history, and it has made such research far more difficult. From my experience interacting with archaeologists, anthropologists, and museum directors who focus on Native American prehistory, it is clear to me that many feel a deep sense of loss about the return of collections of scientifically important bones, and wish to keep them in the possession of museums while acknowledging the dubious ways in which many of these collections were assembled in the course of U.S. expropriation of Native American lands.²² Balanced against this is the sense of loss that many Native Americans feel about having ancestors’ remains disturbed. To navigate these competing interests and the law, many museums employ “NAGPRA officers” whose job it is to identify cultural and skeletal remains that can be associated with particular Native American tribes and to reach out to representatives of those tribes in order to return the items. But while the NAGPRA officers with whom I have interacted are dedicated to fulfilling the letter of the law and do so professionally, they are also careful to not go beyond it. They feel distressed when, as in the case of Kennewick Man, remains are returned to tribes without the evidence of biological or cultural connection that NAGPRA regulations require.

埃斯克·威勒斯列夫是一位在这一领域取得突破性进展的遗传学家。他不仅利用肯纳威克样本，还利用其他土著居民的骨骼遗骸提取DNA，以一种创新而巧妙的方式赢得了土著社区的合作——尽管这并非让考古和博物馆界的每个人都满意。他意识到，土著社区和遗传学家之间可以存在共同利益，因为DNA研究能够赋予部落对其遗骸提出所有权主张的权利。从大约一百具遗骸中提取的基因组序列就证明了这一点。一份距今约13000年的澳大利亚原住民头发样本 ^{23 、一具近13000年前的克洛维斯人骨骼 24}以及一具约8500年前的肯纳威克人骨骼 ²⁵ 。在这三个案例中，威勒斯列夫都是在获得DNA后直接与相关部落接洽，而不是通过诸如《美国原住民坟墓保护和归还法案》（NAGPRA）等机构主导的流程与他们进行沟通。

One geneticist who is breaking new ground in this area is Eske Willerslev. Not only with the Kennewick sample but also with other indigenous skeletal remains from which he has assembled DNA, Willerslev has won the cooperation of indigenous communities in a way that is innovative and brilliant—even if it is not making everyone in the archaeological and museum community happy. He has realized that there can be shared interests between indigenous communities and geneticists because DNA studies can empower tribes to stake claims on remains. This happened in the case of the genome sequences extracted from an approximately one-hundred-year-old Australian Aboriginal hair sample,²³ the almost thirteen-thousand-year-old Clovis skeleton,²⁴ and the approximately eighty-five-hundred-year-old Kennewick skeleton.²⁵ In all three cases, Willerslev approached tribes directly after obtaining DNA, instead of engaging them through an institutionally run process such as the ones that have been set up through NAGPRA.

尽管考古界许多人对威勒斯列夫在正式体制外与部落接触的做法表示担忧，但他在某些方面取得了成功。在澳大利亚，他与原住民群体就百年毛发样本的研究开展的合作赢得了他们的好感，并为他与同事于2016年发表的关于当代原住民人口的更为宏大的研究铺平了道路。 ²⁶ 同样，在美国，威勒斯列夫在克洛维斯和肯纳威克遗址中与原住民群体的合作也有助于建立良好的关系，并鼓励部落支持对其他遗骸进行古代DNA分析。

Although many in the archaeological community have been concerned about Willerslev’s approach of engaging tribes outside the formal institutional process, he has been successful in several ways. In Australia, his engagement with Aboriginal groups in the context of his work on the hundred-year-old hair sample generated goodwill and opened the door to a much more ambitious study of present-day Aboriginal populations published in 2016 by him and colleagues.²⁶ Similarly, in the United States, Willerslev’s engagement with indigenous groups in the Clovis and Kennewick cases has helped generate goodwill and encouraged tribes to support ancient DNA analysis of other remains.

犹他州灵洞发现的遗骸便是这一进展的一个显著例证。2000年，美国土地管理局决定不将这些近11000年前的遗骸归还给提出归还请求的法伦派尤特-肖肖尼部落。该局的决定依据是，没有证据表明这些遗骸与该部落存在生物学或文化上的联系。随后，该部落提起诉讼，使这些遗骸陷入法律僵局，只能出于研究其祖先、确定其是否确实与法伦派尤特-肖肖尼部落存在生物学联系的目的对其进行调查。2015年10月，肯纳威克论文发表后，威勒斯列夫获准对这些遗骸进行古代DNA分析。大约一年后，他向土地管理局提交了一份技术报告，表明该个体的祖先与现代美洲原住民完全来自同一远古血统。基于这份报告，土地管理局决定将遗骸归还给该部落。 ²⁷

A remarkable example of this progress is provided by remains found in Spirit Cave in Utah. In 2000, the U.S. Bureau of Land Management decided against returning these almost eleven-thousand-year-old remains to the Fallon Paiute-Shoshone tribe that requested them. The bureau’s basis for the decision was that there was no evidence of biological or cultural connection to that tribe. The tribe then sued, putting the remains into a legal limbo that allowed them to be investigated only for the purpose of studying their ancestry to determine whether they indeed might have a biological connection to the Fallon Paiute-Shoshone. In October 2015, after publication of the Kennewick paper, Willerslev was given access to the remains for ancient DNA analysis, and around a year later he delivered to the bureau a technical report showing that the individual had ancestry that was entirely from the same deep lineage as present-day Native Americans. On the basis of this report, the bureau decided to return the bones to the tribe.²⁷

这一决定令我联系过的NAGPRA官员感到困惑，他指出，这种解释超出了NAGPRA法律的字面意思，该法律要求的是证明与法伦派尤特-肖肖尼族而非其他族群的联系，而威尔威尔斯列夫显然没有提出过这样的论证。但当我与威尔斯列夫谈到将样本归还部落时，他认为《美国原住民坟墓保护和归还法案》（NAGPRA）的条文并不那么重要，即使法律尚未完全更新，社区的标准也在发生变化。在《自然》杂志一篇关于归还灵洞遗骸决定的文章中，人类学家丹尼斯·奥罗克被引述说，该案例为如何让美洲原住民群体参与到利用遗传学来确定哪些遗骸需要研究和重新安葬的行动中树立了榜样。人类学家金·塔尔贝尔指出，灵洞的例子表明，部落和科学家之间的关系并非必然是对抗性的：“部落不喜欢被强加科学的世界观……但他们对科学本身是感兴趣的。” ²⁸

This decision confused the NAGPRA officer I corresponded with about it, who noted that the interpretation was beyond the letter of the NAGPRA law, which required documentation of a connection to the Fallon Paiute-Shoshone more than to other groups, which Willerslev had apparently not demonstrated. But when I talked with Willerslev about returning samples to tribes, his view was that the letter of the NAGPRA law was not so important and that the community standard was changing even if the law had not yet caught up. In an article in the scientific journal Nature about the decision to return the Spirit Cave remains, the anthropologist Dennis O’Rourke was quoted as saying that the case set an example for how Native American groups could be engaged in using genetics to determine which remains to study and rebury. The anthropologist Kim TallBear pointed out how the Spirit Cave example showed that the relationship between tribes and scientists need not be antagonistic: “Tribes do not like having a scientific world view politically shoved down their throat…but there is interest in the science.”²⁸

威勒斯列夫意识到，古代 DNA 数据提供了一种证据，可以用来确立博物馆收藏中不属于任何家族的遗骸的归属权，这为打破学者和土著社区之间长期存在的不良关系提供了一个意想不到的机会。

Willerslev’s realization that ancient DNA data provide a type of evidence that can be used to establish claims on unaffiliated remains held in museum collections offers an unexpected opportunity to begin to break the logjam of poor relations that has built up between scholars and indigenous communities.

美洲原住民和遗传学家之间还有第二个尚未实现的共同目标——利用古代DNA，通过分析古代样本基因组的变异，来估算1492年以前美洲原住民的人口规模。这对美洲原住民来说至关重要，因为有证据表明，在欧洲人到来以及随之而来的流行病浪潮之后，美洲的人口规模骤减了约十倍，导致先前建立的复杂社会瓦解。欧洲殖民者抵达美洲时发现的相对较小的人口规模，被用来为吞并美洲原住民的土地提供道德上的正当理由。欧洲殖民者有意淡化对美洲原住民人口规模的估计，声称在欧洲人到来之前，美洲几乎没有文明或高度发达的人群。 ²⁹

There is also a second great area of unrealized common cause between Native Americans and geneticists—the potential to use ancient DNA to measure the sizes of populations that existed prior to 1492 by looking at variation within the genome of ancient samples. This is a critical issue for Native Americans, as there is evidence for about a tenfold collapse in population size in the Americas following the arrival of Europeans and the waves of epidemic disease that Europeans brought, leading to the dissolution of previously established complex societies. The relatively small population sizes that European colonialists encountered when they arrived in the Americas were used to provide moral justification for the annexation of Native American lands. The European colonialists had an interest in minimizing the estimates of Native American population sizes, of claiming that there were few if any civilizations or sophisticated populations in the Americas before Europeans came.²⁹

我希望随着基因组革命的影响被更广泛地认识到，原住民能够越来越意识到DNA如何成为连接当代美洲原住民与其根源以及彼此之间的工具。但这并不能解决所有问题。美洲原住民伦理学家和社区领袖表达了他们的担忧，但这或许有助于减少对抗，促进未来的相互理解甚至合作。

I hope that as the consequences of the genome revolution are more broadly realized, indigenous people will increasingly recognize how DNA can become a tool to connect present-day Native American people to their roots and to each other. This will not solve all the concerns that Native American ethicists and community leaders have articulated, but it may serve to reduce antagonism and promote greater understanding and even collaboration in the future.

美洲原住民的基因证据

The Genetic Evidence of the First Americans

2012年，我的实验室发表了首个针对美洲原住民人口历史的全基因组研究，其中包含了52个不同族群的数据。这项研究的一个主要局限在于，由于当时人们对美洲原住民的基因研究存在担忧，我们完全没有来自美国本土48个州的样本。尽管如此，这项研究仍然涵盖了西半球其他大部分地区的美洲原住民多样性，并为我们了解他们的过去提供了新的视角。 ³⁰

The first genome-scale study of Native American population history came in 2012, when my laboratory published data on fifty-two diverse populations. A major limitation of the study was that we had no samples at all from the lower forty-eight states of the United States because of anxieties about genetic research on Native Americans. Nevertheless, the study sampled Native American diversity in much of the rest of the hemisphere, and provided new insights about the past.³⁰

我们研究的大多数个体在过去五百年间都从非洲或欧洲祖先那里获得了少量基因组，这反映了自欧洲殖民者到来以来发生的深刻变革。我们对许多没有此类混合证据的个体进行了大量分析，但对于某些人群，尤其是在加拿大，我们抽样的所有个体都至少有一些非美洲原住民血统。由于我们希望将这些人群纳入研究范围，我们采用了一种能够识别个体基因组中哪些部分源自欧洲或非洲的技术。我们通过寻找基因组中较长的片段来实现这一点，这些片段中，个体携带的基因变异在非洲人和欧洲人中频率很高，但在美洲原住民中频率很低。屏蔽这些基因组片段有助于我们揭开美洲五百年来混合的历史，从而了解欧洲人到来之前美洲原住民人口关系的结构。

Most of the individuals we studied derived small fractions of their genomes from African or European ancestors in the last five hundred years, reflecting the profound upheavals that have occurred since the arrival of European colonists. We carried out many analyses on individuals with no evidence of such mixture, but for some populations, especially in Canada, all the individuals we sampled had at least some non–Native American ancestry. Because we wanted to include these populations, we used a technique that allowed us to identify which sections of people’s genomes were of European or African origin. We did this by searching for extended genomic stretches in which individuals carried genetic variants at high frequency in Africans and Europeans but at low frequency in Native Americans. Masking out these sections of the genome helped us to peel back the history of five hundred years of admixture in the Americas to understand something about what the structure of Native American population relationships was like before European contact.

我们使用四群体检验法比较了所有可能的北美原住民群体组合。我们用此检验法评估欧亚人群（例如汉族）是否与某个北美原住民群体共享更多基因突变，并检验了所有可能的群体组合。对于47个……在对52个族群的研究中，我们未能发现他们与亚洲人的亲缘关系存在差异。这表明，当今绝大多数美洲原住民，包括墨西哥以南的所有族群以及加拿大东部的族群，都源自同一个共同祖先。（其余五个族群，均来自北极地区或阿拉斯加和加拿大的太平洋西北沿岸，也显示出来自不同祖先的证据。）因此，如今美洲原住民群体之间显著的体质差异，并非源于来自欧亚大陆不同地区的移民，而是源于他们自共同祖先群体分化以来的进化。我们将这个共同祖先群体称为“第一批美洲人”。

We compared all possible pairs of Native American populations using the Four Population Test. We used this test to evaluate whether Eurasian populations—for instance, Han Chinese—shared more genetic mutations with one Native American population or another, testing all possible pairs of populations. For forty-seven of the fifty-two populations, we could not detect differences in their relatedness to Asians. This suggested to us that the vast majority of Native Americans today, including all those from Mexico southward as well as populations from eastern Canada, descend from a single common lineage. (Five remaining populations, all from the Arctic or from the Pacific Northwest coast of Alaska and Canada, also had evidence of ancestry from different lineages.) Thus the extraordinary physical differences among Native American groups today are due to evolution since splitting from a common ancestral population, not to immigration from different sources in Eurasia. We called this common ancestral population the “First Americans.”

我们假设，我们所描述的“第一批美洲人”谱系代表了最早迁徙到冰盖以南的人群的后裔，无论他们是通过无冰走廊还是沿海路线迁徙而来。迄今为止的基因组研究尚无法确定这个群体的规模有多小，也无法确定他们迁徙了多少代。但无论如何，我们认为这是一个规模有限的先驱群体，他们迁徙到人类分布空白的区域，并在所到之处迅速扩张。

We hypothesized that the “First American” lineage that we had characterized represented the descendants of the first people to spread south of the ice sheets, whether via an ice-free corridor or along a coastal route. Genomic studies so far have not been able to determine how small this group was or how many generations it wandered. But whatever happened, we were arguing that this was a pioneer population of limited size that moved into a human vacuum, expanding dramatically wherever it arrived.

遗传数据从宏观上支持了这一假设的正确性。我们反复运用四群体检验法，逐渐发现，从北美北部到南美南部，绝大多数美洲原住民群体都可以被大致描述为同一棵树的不同分支，这与欧亚大陆的人口关系模式形成了鲜明对比。大多数群体都从中心主干上清晰地分化出来，之后几乎没有发生混合。分化大致呈南北走向，这与人口向南迁徙时，各个群体逐渐分离并定居下来，此后一直大致保持在同一地点的观点相符。这一模式最显著的例外是，在蒙大拿州靠近如今加拿大边境的地方发现的，与克洛维斯文化相关的婴儿，距今不到一万三千年。这名克洛维斯婴儿的血统与如今邻近加拿大居民的血统不同，这反映了后来发生的大规模人口迁徙。

The genetic data provide support for the correctness of this hypothesis in its broad outlines. As we applied the Four Population Test time and again, it became clear to us that the great majority of Native Americans, from populations in northern North America down to southern South America, can be broadly described as branches of one tree, forming a sharp contrast to patterns of population relationships in Eurasia. Most populations branched cleanly off the central trunk with little subsequent mixture. The splits proceeded roughly in a north-to-south direction, consistent with the idea that as populations traveled south, groups peeled off and settled, remaining in approximately the same place ever since. The most striking exception to this pattern was the less than thirteen-thousand-year-old infant associated with the Clovis culture who was found in Montana very close to the present-day Canadian border. The Clovis infant came from a lineage different from that of present-day inhabitants of neighboring Canada, reflecting major population movements that must have happened later.

在美洲的一些地方，古代DNA证实了这样一种理论：人口已经在同一地区生活了数千年。根据我们和拉尔斯·费伦-施密茨（Lars Fehren-Schmitz）对距今九千年的秘鲁人进行的分析，该地区的美洲原住民群体一直保持着广泛的连续性。我们研究过的所有秘鲁古代基因组，彼此之间以及与当今讲克丘亚语和艾马拉语的秘鲁原住民的亲缘关系，都比与任何其他当今南美洲人群的亲缘关系更近。我们在距今约八千年的阿根廷南部美洲原住民和距今约一万年的巴西南部美洲原住民身上也发现了类似的现象。同样的情况也适用于不列颠哥伦比亚省附近岛屿上的美洲原住民，他们似乎是一个连续存在了约六千年的群体，即使当地的连续性无法追溯到一万年前。^所有这些群体都与今天生活在同一地区的美洲原住民的亲缘关系，比与远在异地的美洲原住民的亲缘关系更近。

In some places in the Americas, ancient DNA confirms the theory that populations have remained in the same region for thousands of years. According to analyses we and Lars Fehren-Schmitz have done of Peruvians dating up to nine thousand years ago, there has been broad continuity in Native American populations in this region. All the ancient genomes from Peru that we have studied are more closely related to each other and to present-day Native Americans from Peru who speak the Quechua and Aymara languages than they are to any other present-day South American populations. We have similar findings from Native American individuals from southern Argentina dating to around eight thousand years ago, and Native American individuals from southern Brazil dating to around ten thousand years ago. The same applies to Native Americans from the islands off British Columbia, who appear to have been part of a continuous population for around six thousand years, even if the local continuity does not clearly go back more than ten thousand years.³¹ All are more closely related to Native Americans who live in the same regions today than to Native Americans far away.

约瑟夫·格林伯格的基因组康复

The Genomic Rehabilitation of Joseph Greenberg

对美洲原住民迁徙路线的基因发现也有助于解决一个语言学上的争议。早在十七世纪，人们就注意到美洲原住民语言的非凡多样性，一些欧洲传教士将其归因于魔鬼的阻挠，认为魔鬼使传教士用来向一个族群传教的语言无法用于向另一个族群传教，从而阻碍了原住民的皈依。语言学家可以分为“语言分裂者”和“语言归并者”。“语言分裂者”强调语言之间的差异，而“语言归并者”则强调语言的共同起源。莱尔·坎贝尔是语言分裂者中最极端的代表之一，他将大约一千种美洲原住民语言划分为大约两百个语系（相关语言的群体），有时甚至将语系划分到特定的河谷地区。³²约瑟夫·格林伯格是语言归并者中最极端的代表之一，他认为所有美洲原住民语言都可以归为三个语系，并且他能够追溯这三个语系之间的深层联系。他认为这三个语系反映了来自亚洲的三次大规模移民浪潮。

The genetic discovery of the spread of the First Americans also helps to resolve a linguistic controversy. The extraordinary diversity of Native American languages had been noted as early as the seventeenth century, with some European missionaries attributing it to the devil’s efforts to resist the conversion of Native populations by making the language that missionaries needed to learn to proselytize to one population useless for proselytizing to the next. Linguists can be divided into “splitters,” who emphasize differences among languages, and “lumpers,” who emphasize their common roots. One of the most extreme splitters was Lyle Campbell, who divided about one thousand Native American languages into about two hundred families (groups of related languages), sometimes even localized to particular river valleys.³² One of the most extreme lumpers was Joseph Greenberg, who argued that he could group all Native American languages into just three families, the deep connections of which he could trace. He argued that these three families reflected three great waves of migration from Asia.

坎贝尔和格林伯格在对美洲原住民语言关系的解读上曾有过著名的争论，坎贝尔认为格林伯格的三元分类法非常令人反感，以至于他在1986年写道，格林伯格的分类“应该被驳斥”。 ³³事实上，其中两个语系是无可争议的：爱斯基摩-阿留申语系，西伯利亚、阿拉斯加、加拿大北部和格陵兰岛的许多土著民族都使用这种语言；以及纳-德内语系，居住在北美北部太平洋沿岸、加拿大北部内陆和美国西南部的部分美洲原住民部落都使用这种语言。

Campbell and Greenberg clashed famously in their interpretation of Native American language relationships, with Campbell finding Greenberg’s tripartite classification so objectionable that he wrote in 1986 that Greenberg’s classification “should be shouted down.”³³ In fact, two of the language families are indisputable: Eskimo-Aleut languages spoken by many of the indigenous peoples of Siberia, Alaska, northern Canada, and Greenland, and Na-Dene languages spoken by a subset of the Native American tribes living on the Pacific coast of northern North America, in the interior of northern Canada, and in the southwestern United States.

但格林伯格提出的第三个语系——“美洲印第安语族”（Amerind）——却遭到了众多语言学家的质疑。他声称该语系包含了大约90%的美洲原住民语言。格林伯格提出美洲印第安语族的方法是研究不同美洲原住民语言中的数百个词汇，并根据它们的共享程度进行评分。他通过发现高共享率，声称这是共同起源的证据。在他看来，冰盖以南的第一批美洲人使用的就是原始美洲印第安语。由于他发现，根据这种方法，美洲所有非纳-德内语族和非爱斯基摩-阿留申语族的语言都可以被归类为美洲印第安语族，因此他得出​​结论：语言数据支持美洲原住民从亚洲三次大规模迁徙的理论。如果存在第三次迁徙，那么就会留下另一套截然不同的语言体系。

But it was Greenberg’s third family, “Amerind,” which he claimed includes about 90 percent of the languages of Native Americans, that so many linguists found objectionable. The method that Greenberg used to propose Amerind was to study several hundred words across different Native American languages and to score them according to the extent to which they were shared. By finding high rates of sharing, he claimed evidence for common origin. As he saw it, proto-Amerind was spoken by the first Americans south of the ice sheets. Because he found that every non-Na-Dene and non-Eskimo-Aleut language throughout the Americas could be classified as Amerind using this approach, he concluded that the language data supported a theory of three great waves of Native American dispersal from Asia. If there had been another wave, it would have left another distinct set of languages.

随后对格林伯格观点的批判可谓是尖锐无比。批评者认为，他列举的词汇过于简短，不足以证明词汇之间的共性。他们还质疑这些词汇是否真的源于共同的词根。人们普遍认为，由于语言变化迅速，在几千年以上的时间跨度内识别共同词汇会变得十分困难，但格林伯格却声称在两倍于此的时间跨度内发现了词汇之间的联系。

The critique of Greenberg’s ideas that followed was withering. Critics argued that the list of words was too brief to establish commonality. Critics also disputed the claim that these words truly stemmed from common roots. Identification of shared words is thought to become difficult for time depths of more than a few thousand years because languages change so fast, but Greenberg was claiming to detect links at twice this time depth.

但格林伯格说对了一点。他划分的美洲印第安人类别几乎与遗传学发现的第一批美洲人类别完全吻合。他根据语言预测的亲缘关系最近的人群群体，实际上也得到了现有数据人群遗传模式的验证。而如今美洲原住民语言的分裂也反映了这样一种历史：绝大多数人群都源自同一个祖先。迁徙扩散。任何观察美洲语言分布图的人都会发现，其形态与欧亚大陆或非洲截然不同。美洲数十个语系局限于狭小的区域，而欧亚大陆和非洲则拥有广袤的地域，居住着使用印欧语系、南岛语系、汉藏语系和班图语系等密切相关语言的人们。这些语系都反映了大规模迁徙和人口更替的历史。美洲的第一次扩张似乎如此迅速，以至于该大陆的各种语言之间存在着一种耙状的结构，许多分支平行地延伸到一个共同的根部，而这个根部可以追溯到美洲早期定居时期附近。 ³⁴因此，遗传学和语言学证据都支持这样一种观点：许多现代美洲原住民是早期人类定居美洲大陆后不久生活在同一地区的族群的直系后裔。这表明，在最初的扩散之后，美洲的人口更替频率比非洲和欧亚大陆要低。

But Greenberg got something right. His category of Amerind corresponds almost exactly to the First American category found by genetics. The clusters of populations that he predicted to be most closely related based on language were in fact verified by the genetic patterns in populations for which data are available. And the present-day balkanization of Native American languages also reflects a history in which the great majority of populations descend from a single migratory spread. Anyone looking at a language map of the Americas can see that its appearance is qualitatively different from that of Eurasia or Africa, with dozens of language families restricted to small territories, compared to the vast swaths of territory in Eurasia and Africa inhabited by people who speak closely related tongues in the Indo-European, Austronesian, Sino-Tibetan, and Bantu language families, each of which reflects a history of mass migrations and population replacements. The First American expansion seems to have been so fast that the languages of the continent are related by a rake-like structure with many tines extending in parallel to a common root that dates close to the time of the early settlement of the Americas.³⁴ So both the genetic and linguistic evidence support a scenario in which many of the present-day Native American populations are direct descendants of populations that plausibly lived in the same region shortly after the first peopling of the continent. This suggests that after the initial dispersal, population replacement was more infrequent in the Americas than it was in Africa and Eurasia.

虽然基因数据在很大程度上证实了格林伯格的总体观点，但他忽略了一些重要的东西。尽管爱斯基摩-阿留申语系和纳-德内语系的使用者在基因上存在差异，但他们的亲缘关系却截然不同。虽然他们与其他美洲原住民的区别在于其祖先来自亚洲不同的迁徙路线，但两者都拥有大量的美洲原住民血统：在我们研究的爱斯基摩-阿留申语使用者中，这一比例约为60%；而在一些纳-德内语使用者中，这一比例约为90%。 ³⁵因此，尽管格林伯格预测的三个语言群体与三个古代人群高度吻合，但美洲原住民对当今美洲所有土著民族的人口构成做出了主导性贡献。

While the genetic data provided a large measure of confirmation for Greenberg’s broad picture, he missed something important. Although Eskimo-Aleut and Na-Dene speakers are genetically distinguishable from other Native Americans because they carry ancestry from distinct streams of migration from Asia, both have large amounts of First American ancestry: around a 60 percent mixture proportion in the case of the Eskimo-Aleut speakers we studied, and around a 90 percent proportion in the case of some Na-Dene speakers.³⁵ So while Greenberg’s three predicted language groups correlate well with three ancient populations, First Americans have made a dominant demographic contribution to all present-day indigenous peoples in the Americas.

Y人口

Population Y

从遗传牌堆中抽出的下一张牌完全出乎我们的意料——至少对我们遗传学家来说是这样。

The next card dealt from the genetic deck was a complete surprise—at least to us geneticists.

一些研究人类骨骼形态的体质人类学家多年来一直声称，一些距今一万年前的美洲骨骼，其形态与人们通常认为的现代美洲原住民祖先的骨骼并不相符。其中最具代表性的当属卢西亚（Luzia），这具距今约11500年的骨骼于1975年在巴西拉帕韦尔梅利亚（Lapa Vermelha）被发现。许多人类学家认为，她的面部形状更接近澳大利亚和新几内亚的土著居民，而非古代或现代东亚人，亦或是美洲原住民。这一谜题引发了人们的猜测：卢西亚可能来自一个早于美洲原住民的族群。人类学家沃尔特·内维斯（Walter Neves）已经鉴定出数十具中美洲和南美洲的骨骼，他称之为“古美洲”形态。内维斯最主要的例证是一组55个头骨，其年代可追溯到一万年前或更久远，这些头骨发现于巴西拉戈阿圣塔（Lagoa Santa）的一个史前垃圾场。³⁶

Some physical anthropologists studying the shapes of human skeletons had for years been asserting that there are some American skeletons, dating to before ten thousand years ago, that do not look like what one would expect for the ancestors of today’s Native Americans. The most iconic is Luzia, an approximately 11,500-year-old skeleton whose remains were found in Lapa Vermelha, Brazil, in 1975. Many anthropologists find the shape of her face more similar to those of indigenous peoples from Australia and New Guinea than to those of ancient or modern peoples of East Asia, or Native Americans. This puzzle led to speculation that Luzia came from a group that preceded Native Americans. Anthropologist Walter Neves has identified dozens of Mesoamerican and South American skeletons with what he calls a “Paleoamerican” morphology. Exhibit number one for Neves is a set of fifty-five skulls dating to ten thousand years ago or more from a prehistoric garbage dump at Lagoa Santa in Brazil.³⁶

这些说法存在争议。形态特征会因饮食和环境而异，人类抵达美洲后，自然选择以及随着时间推移在人群中积累的随机变化都可能导致了形态的改变。肯纳威克人的经历或许可以佐证这一点，他的骨骼形态与环太平洋地区人群的骨骼形态有相似之处，但……^{从基因上看}，他们与其他美洲原住民完全源自同一祖先群体，这无疑是一个重要的警示——一个关于将形态学解读为群体关系强有力证据的危险性的活生生的例子。37许多人批评内维斯，认为他的分析存在统计学缺陷，因为他为了强化其古美洲人理论而选择性地纳入某些遗址，并故意排除那些不符合其理论的遗址，这种做法与严谨的科学原则相悖。

These claims are controversial. Morphological traits vary depending on diet and environment, and after the arrival of humans in the Americas, natural selection as well as random changes that accumulate in populations over time may have contributed to morphological change. The experience of Kennewick Man, whose skeleton has morphological affinities to those of Pacific Rim populations but genetically is derived entirely from the same ancestral population as other Native Americans, serves as a great warning—an object lesson about the danger of interpreting morphology as strong evidence of population relationships.³⁷ Many have criticized Neves by suggesting that his analyses were statistically flawed, in that he chose which sites to include in his analysis in order to strengthen his Paleoamerican idea and deliberately left out those that did not fit, an approach inconsistent with rigorous science.

尽管如此，庞图斯·斯科格伦德还是决定更仔细地研究美洲原住民的基因数据，寻找与早期美洲人不同的祖先痕迹。他的逻辑是这样的：如果这片大陆上曾经存在被早期美洲人驱逐的古代居民，他们可能与现代人群的祖先有过基因交流，从而在当今人类的基因组中留下一些统计信号。

Nonetheless, Pontus Skoglund decided to inspect Native American genetic data more closely, looking for traces of ancestry different from the First Americans. His logic went as follows. If there were ancient people on the continent who were displaced by First Americans, they may have mixed with the ancestors of present-day populations, leaving some statistical signal in the genomes of people living today.

斯科格伦德进行了一项四群体检验，以比较我们之前已知的来自美洲的所有可能的群体对。他曾认为，美洲以外的所有人群，包括澳大拉西亚原住民（包括安达曼群岛居民、新几内亚人和澳大利亚人）以及其他一些人类学家推测与古美洲人相关的人群，都完全具有美洲原住民的血统。他发现，来自巴西亚马逊地区的两个美洲原住民群体，与澳大拉西亚人的亲缘关系比与其他世界人群更近。斯科格伦德以博士后研究员的身份加入我的实验室后，在环绕亚马逊盆地的其他美洲原住民群体中，发现了与澳大拉西亚人较弱但可能仍然存在的遗传亲缘关系信号。他估计，这些人群中古代血统的比例很小——1%到6%——其余部分与美洲原住民的血统一致。 ³⁸

Skoglund undertook a Four Population Test to compare all possible pairs of populations from the Americas that we had previously thought were entirely of First American ancestry to all possible pairs of populations outside the Americas, among them indigenous people from Australasia (including Andaman Islanders, New Guineans, and Australians) and other populations hypothesized by some anthropologists to be related to Paleoamericans. He found two Native American populations, both from the Amazon region of Brazil, that are more closely related to Australasians than to other world populations. After joining my laboratory as a postdoctoral scientist, Skoglund found weaker signals of genetic affinity to Australasians, but still probably real, in other Native American populations ringing the Amazon basin. He estimated that the proportion of ancient ancestry in these populations was small—1 to 6 percent—with the rest being consistent with First American ancestry.³⁸

起初，我和斯科格伦德对这些发现持怀疑态度，但统计证据却越来越有力。我们在多个独立收集的数据集中都观察到了相同的模式。我们还证明，这些模式不可能是近期亚洲人口迁徙的结果——虽然亚马逊人与澳大利亚、新几内亚和安达曼群岛的土著居民（以东亚人为基准）的亲缘关系最密切，但他们与这些地区的任何一个群体都不算特别亲近。基因数据也否定了波利尼西亚人从太平洋迁徙到美洲的说法。虽然在过去几千年里，随着波利尼西亚人掌握了跨洋航行技术，这种迁徙完全有可能发生，但我们发现的亲缘关系与波利尼西亚人没有任何共同之处。这看起来更像是古代人群迁徙到美洲的证据，而这个人群与澳大利亚人、新几内亚人和安达曼人的亲缘关系比与现代西伯利亚人的亲缘关系更近。我们得出结论，我们发现了一个“幽灵”人群的证据：一个不再以纯种形式存在的人群。我们把这个群体称为“Y 群体”，取自图皮语中的“ ypykuéra”，意思是“祖先”。图皮语是拥有这种血统比例最高的人群的语言语系。

Skoglund and I were initially skeptical about these findings, but the statistical evidence just kept getting stronger. We saw the same patterns in multiple independently collected datasets. We also showed that these patterns could not arise as a result of recent migrations from Asian populations—while Amazonians had their strongest affinity to indigenous people from Australia, New Guinea, and the Andaman Islands (compared to East Asians as a baseline), they were not particularly close to any of them. Also contradicted by the genetic data was a Polynesian migration from the Pacific across to the Americas. While such a migration could have reasonably occurred over the past couple of thousand years as Polynesians mastered the technology of transoceanic travel, the affinities we found had nothing in common with Polynesians. It really looked like evidence of a migration into the Americas of an ancient population more closely related to Australians, New Guineans, and Andamanese than to present-day Siberians. We concluded that we had found evidence of a “ghost” population: a population that no longer exists in unmixed form. We called this “Population Y” after the word ypykuéra, meaning “ancestor” in Tupí, the language family of the populations with the largest proportions of this ancestry.

我们在图皮语族群中发现了最多的Y族血统，他们就是苏鲁伊人，也就是本章开头提到的起源神话的作者。他们现在大约有1400人，居住在巴西朗多尼亚州。39^他们一直以来苏鲁伊人相对孤立，直到20世纪60年代道路建设者途经其领地时才与巴西政府建立正式关系。自那时起，苏鲁伊人便开始捍卫自己的土地免遭森林砍伐，接管咖啡种植园，并举报非法伐木者和采矿者。他们寻求美国原住民权利组织的代表，并因其保护的热带雨林所减少的温室气体排放而申请碳信用额度。

The Tupí-speaking population in which we found the most Population Y ancestry was the Suruí, the authors of the origin myth that begins this chapter. They now number about fourteen hundred people and live in the Brazilian state of Rondônia.³⁹ They have been relatively isolated, establishing formal relations with the government of Brazil only in the 1960s when road builders came through their territory. Since then, the Suruí have defended their land from deforestation, taken over coffee plantations, and reported illegal loggers and miners. They have sought representation from indigenous rights groups in the United States and claimed carbon credits for the greenhouse gases conserved through the rainforest they have protected.

我们发现Y族血统的另一个图皮语系族群是卡里蒂亚纳人。本章开头讨论了卡里蒂亚纳人，他们是最早积极反对基因研究的美洲原住民部落之一——他们反对基因研究的原因是，1996年采集了他们的DNA样本，当时承诺改善他们的医疗保健，但这一承诺从未兑现。卡里蒂亚纳人约有三百人，也来自朗多尼亚州。我们分析的样本并非来自那次有争议的1996年采样，而是来自1987年的一次采样，那次采样似乎遵循了当时的伦理标准，并获得了知情同意。我希望看到我们研究结果的卡里蒂亚纳人能够欢迎这些关于他们独特血统的发现，并将其视为一项积极的发现，凸显了参与科学研究的益处^。40

Another group belonging to the Tupí language family in which we found Population Y ancestry is the Karitiana. The Karitiana are discussed at the beginning of this chapter as one of the first Native American tribes to become active in protesting against genetic research—in their case because of concern that DNA samples had been taken from them in 1996 with a promise of improved access to health care that has never been realized. The Karitiana are around three hundred strong and also come from Rondônia. The samples we analyzed were not part of this tainted 1996 sampling but instead from a 1987 sampling in which informed consent procedures consistent with the ethical standards of the time appear to have been followed. I hope that the Karitiana individuals who encounter our findings will welcome these observations about their distinctive ancestry as a positive discovery that highlights benefits that can come from engaging in scientific studies.⁴⁰

我们发现大量Y族血统的第三个族群是沙万特人，他们讲格语族语言，这与苏鲁伊人和卡里蒂亚纳人讲的图皮语族语言不同。他们大约有18000人，居住在巴西马托格罗索州的高原上。他们曾被迫迁徙，如今他们的土地遭受环境破坏，他们的传统生活方式也不断受到开发的威胁。 ⁴¹

The third population in which we found substantial Population Y ancestry is the Xavante, who speak a language of the Ge group, which is different from the Tupí language group spoken by the Suruí and Karitiana. They number around eighteen thousand people and are located in Brazil’s Mato Grosso state, on the Brazilian plateau. They have been forcibly relocated, their land today suffers from environmental degradation, and their indigenous way of life is constantly under threat from development.⁴¹

我们在中美洲或安第斯山脉以西的南美洲地区几乎没有发现Y人群的祖先成分。我们也没有在美国北部克洛维斯文化婴儿的近13000年前的基因组中，或在当今加拿大阿尔冈昆语使用者中检测到Y人群的祖先成分。Y人群的地理分布主要局限于亚马逊地区，这为Y人群的古老起源提供了更多证据。Y族裔人口的祖先分布范围局限于远离白令海峡与亚洲连接线的崎岖地形，这或许符合人们对早期拓荒者群体的预期，他们曾经分布广泛，后来却被其他族群的扩张所边缘化。这种模式与其他一些语系的分布相似——例如，非洲南部科伊桑人使用的图语、克萨语和科伊-夸迪语——这些语系的使用者如同孤岛般散布在崎岖的地形中，周围环绕着说其他语言的人群。

We found little or no Population Y ancestry in Mesoamerica or in South Americans to the west of the high Andes. We also did not detect Population Y ancestry in the almost thirteen-thousand-year-old genome of the Clovis culture infant from the northern United States, or in present-day Algonquin speakers from Canada. The Population Y geographic distribution is largely limited to Amazonia, providing yet more evidence for an ancient origin. The fact that Population Y ancestry is restricted to difficult terrain far from the Bering link to Asia is perhaps what one would expect from an original pioneering population that was once more broadly distributed and was then marginalized by the expansion of other groups. This pattern mirrors the distribution of some other language families—for example, the Tuu, Kx’a, and Khoe-Kwadi languages spoken by the Khoe and San in southern Africa—where islands of these speakers in rugged terrain are surrounded by seas of people speaking other languages.

我们发现的古代谱系最强有力的统计证据出现在巴西——“卢西亚”和拉戈阿圣塔骨骼的发现地——这一事实固然引人注目，但并不能证明我们发现的古代谱系与内维斯等人假设的“古美洲人”形态相吻合。内维斯声称不仅在古代巴西人身上，而且在古代和相对较近的墨西哥人身上也发现了古美洲人的形态，然而我们在墨西哥人身上却没有发现任何蛛丝马迹。此外，埃斯克·威勒斯列夫的研究小组从两个美洲原住民群体中获得了DNA，这两个群体的骨骼形态与内维斯所说的古美洲人典型特征相符：一个是墨西哥西北部下加利福尼亚半岛的佩里库人，另一个是南美洲南端的火地人。这两个群体都不携带Y群体的祖先成分。 ⁴²

The fact that the strongest statistical evidence of the ancient lineage we detect is in Brazil, the home of “Luzia” and the Lagoa Santa skeletons, is remarkable, but does not prove that the ancient lineage we discovered coincides with the “Paleoamerican” morphology hypothesized by Neves and others. Neves claimed to see the Paleoamerican morphology not only in ancient Brazilians but also in ancient and relatively recent Mexicans, and yet we found no hint of a signal in Mexicans. In addition, Eske Willerslev’s group obtained DNA from two Native American groups that had skeletal morphology typical of Paleoamericans according to Neves: Pericúes in the Baja California peninsula of northwestern Mexico and Fuegans in the southern tip of South America. Neither of these groups carried Population Y ancestry.⁴²

那么，这种基因模式意味着什么呢？我们从考古学中已经得知，人类可能在无冰走廊开启之前就已抵达冰盖以南，并在蒙特维德和佩斯利洞穴等考古遗址留下了遗迹。但以克洛维斯人为标志的人口大爆发，仅在无冰走廊开启后才发生。基因数据可能表明，至少有两个截然不同的群体从亚洲迁徙到美洲，他们或许沿着两条不同的路线，在不同的时间迁徙而来。如果Y人群在第一批美洲人之前就已经扩散到南美洲的部分地区，那么在最初的迁徙之后，第一批美洲人很可能进入了Y人群曾经到访过的几乎所有地区，并完全或部分地取代了他们，例如在亚马逊地区。由于亚马逊地区环境相对封闭，Y人群的祖先可能比在其他地方更容易存活下来。这或许可以解释为什么美洲早期人类的祖先在亚马逊地区生存得更好。减缓了美洲原住民向该地区的迁徙速度，使得当地居民能够与新移民融合，而不是简单地被取代。

What, then, does the genetic pattern mean? We already know from archaeology that humans probably arrived south of the ice sheets before the opening of the ice-free corridor, leaving remains at archaeological sites including Monte Verde and the Paisley Caves. But the big population explosion, marked by the Clovis people, only occurred once the ice-free corridor had opened. The genetic data could be giving evidence of early peopling of the Americas by a minimum of two very different groups moving in from Asia, perhaps along two different routes and at different times. If Population Y spread through parts of South America before the First Americans, then it seems likely that after this initial peopling, the First Americans advanced into nearly all of the territories the Population Y people had already visited, replacing them either completely or only partially, as in Amazonia. Population Y ancestry may have survived better in Amazonia than it did elsewhere because of the relative impenetrability of the Amazonian environment. This could have slowed down the movement of First Americans into the region enough to allow people living there to mix with the new migrants rather than simply being replaced.

如今苏鲁伊人身上与澳大拉西亚相关的血统比例很小——与所有非非洲人身上的尼安德特人血统比例大致相同——但忽视其重要性是不明智的。这是因为Y人群对亚马逊人的影响可能远不止2%。Y人群的祖先必须穿越西伯利亚和北美北部广袤的土地，而美洲原住民的祖先也生活在那里。Y人群在开始向南美洲扩张时，很可能已经混入了大量与美洲原住民相关的血统。如果真是如此，那么源自南亚血统的血统就如同Y人群血统的一种“示踪剂”——就像医院里注射到病人静脉中的重金属，用来在CT扫描中追踪血管走向一样。我们估计苏鲁伊人中约有2%的Y族血统，这一估计基于Y族在迁徙过程中未与其他族群发生基因交流的假设。如果我们考虑到他们可能在迁徙途中与美洲原住民相关的族群发生过基因交流，那么苏鲁伊人中Y族的比例可能高达85%，并且仍然能够得出与澳大拉西亚人存在亲缘关系的统计证据。如果实际比例哪怕只有这个数字的一​​小部分，那么美洲原住民向未开垦的处女地扩张的说法就具有极大的误导性。相反，我们应该从美洲一个高度分化的创始族群的扩张角度来思考这个问题。Y族抵达美洲的历史和时间，或许只有通过提取具有Y族血统的骨骼中的古代DNA才能最终确定。

The Australasian-related ancestry in the Suruí today amounts to a small percentage—about the same as the Neanderthal ancestry in all non-Africans—but it would be unwise to dismiss its importance. This is because the impact of Population Y on Amazonians may be much greater than 2 percent. The ancestors of Population Y had to traverse enormous spaces in Siberia and northern North America where the ancestors of First Americans were also living. It is likely that Population Y was already mixed with large amounts of First American–related ancestry when it started expanding into South America. If so, then the ancestry derived from a lineage related to southern Asians is only a kind of “tracer dye” for Population Y ancestry—like the heavy metals injected into patients’ veins in hospitals to track the paths of their blood vessels in a CT scan. Our estimate of around 2 percent Population Y ancestry in the Suruí is based on the assumption that Population Y traversed the entirety of Northeast Asia and America without mixing with other people it encountered. If we allow for the likelihood that there was mixture with populations related to First Americans on the way, the proportion of Population Y in the Suruí could be as high as 85 percent and still produce the observed statistical evidence of relatedness to Australasians. If the true proportion is even a fraction of this, then the story of First Americans expanding into virgin territory is profoundly misleading. Instead, we need to think in terms of an expansion of a highly substructured founding population of the Americas. The history and timing of the arrival of Population Y in the Americas is likely to be resolved only with recovery of ancient DNA from skeletons with Population Y ancestry.

在第一批美国人之后

After the First Americans

基因数据的巨大潜力不仅在于它能告诉我们美洲原住民最深层的起源，还在于它能告诉我们近代以来人口是如何演变成今天这样的。

The great promise of genetic data lies not only in what they can tell us about the deepest origins of Native Americans but also in what genetic data has to say about more recent times and how populations got to be the way they are today.

一个典型的例子是对纳-德内语系使用者起源的深入研究。这些使用者居住在北美太平洋沿岸、加拿大北部部分地区，以及远至美国亚利桑那州的南部地区。语言学家普遍认为，这些语言源于一种不超过几千年的古老语言，它们在北美西北部如此广阔的范围内传播，至少部分是由于人口迁徙所致。2008年，美国语言学家爱德华·瓦伊达(Edward Vajda)的一项惊人发现表明，纳-德内语系与西伯利亚中部叶尼塞语系之间存在更深层次的联系。叶尼塞语系曾被许多族群使用，但如今只有叶尼塞语系中的凯特语仍在日常使用。 ⁴³这些研究结果表明，尽管相隔遥远，但相对较近的一次来自亚洲的迁徙促成了美洲纳-德内语系使用者的出现。

A prime example is insight into the origin of speakers of Na-Dene languages, who live along the Pacific coast of North America, in parts of northern Canada, and as far south as Arizona in the United States. The overwhelming consensus among linguists is that these languages stem from an ancestral language no more than a few thousand years old, and that their dispersal over this vast range in northwestern America must have been driven at least in part by migrations. In an astonishing development in 2008, the American linguist Edward Vajda documented a deeper connection between Na-Dene languages and a language family of central Siberia called Yeniseian, once spoken by many populations, though today only the Ket language of the Yeniseian family is still used on a day-to-day basis.⁴³ These results suggest that despite the enormous distance, a relatively recent migration from Asia gave rise to Na-Dene speakers in the Americas.

遗传学又带来了哪些新信息？我们2012年的研究发现，讲纳-德内语的奇佩维安人拥有一种其他许多美洲原住民所不具备的祖先特征，这为后来的亚洲迁徙理论提供了证据。 ⁴⁴我们估计这种祖先特征仅占奇佩维安人祖先的10%左右，但即便如此，它仍然引人注目。我们想知道，能否利用奇佩维安人身上这种独特的祖先特征作为示踪剂，来记录像奇佩维安人这样的讲纳-德内语的人与过去考古文化中那些可以通过古代DNA进行研究的个体之间的祖先联系。

What new information does genetics add? Our 2012 study found that the Na-Dene-speaking Chipewyan carry a type of ancestry not shared with many other Native Americans, providing evidence for the later Asian migration theory.⁴⁴ We estimated that this ancestry constituted only around 10 percent of Chipewyan ancestry, but it was striking all the same. We wondered whether we could use this distinctive strain of ancestry in the Chipewyans as a tracer dye to document an ancestral link between Na-Dene speakers like Chipewyans and individuals from past archaeological cultures who could be studied with ancient DNA.

2010年，埃斯克·威勒斯列夫及其同事发表了来自格陵兰岛萨卡克文化（格陵兰岛最早的人类文化）一具冰冻个体的约四千年前的头发的全基因组数据。 ⁴⁵他们的分析表明，这名男子的祖先构成与南方的美洲原住民以及随后迁徙到北极的爱斯基摩-阿留申人截然不同。2014年，威勒斯列夫的研究团队进一步扩展了他们的论断，报告了来自几位“古爱斯基摩人”（考古学家对爱斯基摩-阿留申人之前的人群的称呼）的数据。 ⁴⁶所有这些个体都具有广泛的亲缘关系，作者认为他们代表了一次独特的来自亚洲的迁徙，与之前和之后的所有迁徙都不同。他们认为，古爱斯基摩人……大约一千五百年前，随着爱斯基摩-阿留申语系民族的到来，爱斯基摩人基本灭绝，没有留下后代。

In 2010, Eske Willerslev and colleagues published genome-wide data from an approximately four-thousand-year-old lock of hair taken from a frozen individual of the Saqqaq culture, the first human culture of Greenland.⁴⁵ Their analysis showed that this man belonged to a population that had a distinct blend of ancestry compared both to First Americans in the south and the Eskimo-Aleuts who followed them in the Arctic. Willerslev’s group expanded its claim in 2014 when it reported data from several additional “Paleo-Eskimos,” as people who preceded Eskimo-Aleuts are called by archaeologists.⁴⁶ All these individuals were broadly related, and the authors argued that they represented a distinct migration from Asia that was different from all prior and subsequent ones. They argued that the Paleo-Eskimos largely went extinct without leaving descendants after the arrival of Eskimo-Aleut speakers around fifteen hundred years ago.

在2012年的研究中，我们检验了以萨卡克人为代表的古爱斯基摩人是否起源于一次独特的迁徙。出乎意料的是，我们没有发现任何统计学证据支持这一独特的迁徙。相反，我们的检验结果与萨卡克人的祖先可能源自同一来源，而该来源也构成了纳-德内语系奇佩维亚人的祖先，只是比例不同。由于我们从基因数据中得知，如今许多纳-德内语系使用者的祖先中只有约10%来自这次晚期亚洲迁徙，因此很容易理解为什么威勒斯列夫团队使用的聚类分析未能发现与纳-德内语系使用者的联系。我们提出，纳-德内人和萨卡克人可能都拥有部分源自同一次从亚洲到美洲的古代迁徙的祖先。

In our 2012 study, we tested the idea that the Paleo-Eskimos exemplified by the Saqqaq individual were descended from a distinct migration to the Americas. To our surprise, we found no statistical evidence for a distinct migration. Instead, our tests were consistent with the possibility that the Saqqaq derived their ancestry from the same source that contributed to the Na-Dene-speaking Chipewyans, just in different proportions. Since we know from genetic data that only around 10 percent of the ancestry of many Na-Dene speakers today is from this late Asian migration, it is easy to understand why the clustering analysis used by Willerslev’s team missed the connection to Na-Dene speakers. We proposed that the Na-Dene and Saqqaq might both derive part of their ancestry from the same ancient migration from Asia to the Americas.

2017年，帕维尔·弗莱贡托夫、斯特凡·希费尔斯和我证实，古爱斯基摩人的血统并未灭绝，而是延续到了纳-德内人之中。 ⁴⁷通过研究反映近期不同美洲原住民和西伯利亚人群之间基因交流的罕见突变，我们发现了古代萨卡克人和现代纳-德内人之间存在近期共同祖先的证据。事实上，古爱斯基摩人的血统在爱斯基摩-阿留申语使用者到来后灭绝的假设，比我在2012年论文中最初提出的观点更加错误。 ⁴⁸看待现代爱斯基摩-阿留申语使用者祖先的正确方式，是将其视为与古爱斯基摩人和美洲原住民相关的血统的混合体。换句话说，包含古爱斯基摩人的人群远未灭绝，而是以混合形式延续至今，不仅存在于纳-德内人中，也存在于爱斯基摩-阿留申语使用者中。

In 2017, Pavel Flegontov, Stephan Schiffels, and I confirmed that the Paleo-Eskimo lineage did not die out, and instead lives on in the Na-Dene.⁴⁷ By examining rare mutations that reflect recent sharing between diverse Native American and Siberian populations, we found evidence for recent common ancestors between the ancient Saqqaq individual and present-day Na-Dene. In fact, the hypothesis that Paleo-Eskimo lineages went extinct after the arrival of Eskimo-Aleut speakers is even more profoundly wrong than I had originally suggested in my 2012 paper.⁴⁸ The correct way to view the ancestry of present-day speakers of Eskimo-Aleut languages is as a mixture of lineages related to Paleo-Eskimos and First Americans. In other words, far from being extinct, the population that included Paleo-Eskimos lives on in mixed form not just in Na-Dene speakers, but also in Eskimo-Aleut speakers.

我们2017年的研究还揭示了一种全新的、统一的视角，来审视美洲各民族的深层祖先。在这种新的视角下，除了Y人群之外，所有美洲原住民的祖先血统都来自两个祖先谱系：第一批美洲人，以及大约五千年前将小型石器和第一批弓箭带到美洲并建立古爱斯基摩人的群体。 ⁴⁹我们之所以能够证明这一点，是因为在数学上，我们可以用一个模型来拟合数据，其中除亚马逊地区原住民（其祖先属于Y族群）之外的所有美洲原住民，都可以被描述为两个祖先群体的混合体，这两个祖先群体与亚洲人的关系各不相同。这两个祖先群体的混合产生了从亚洲迁徙到美洲的三个源群体，他们分别与爱斯基摩-阿留申语系、纳-德内​​语系以及所有其他语言相关。

Our 2017 work also revealed an entirely new and unifying way to view the deep ancestry of the peoples of the Americas. In this new vision, there were just two ancestral lineages that contributed all Native American ancestry apart from that in Population Y: the First Americans and the population that brought new small stone tools and the first archery equipment to the Americas around five thousand years ago and founded the Paleo-Eskimos.⁴⁹ We could show this because, mathematically, we can fit a model to the data in which all Native Americans excluding Amazonians with their Population Y ancestry can be described as mixtures of two ancestral populations related differentially to Asians. Mixtures of these two ancestral populations produced the three source populations that migrated from Asia to America and that are associated with Eskimo-Aleut languages, Na-Dene, and all other languages.

关于美洲原住民人口历史的第二个基因发现，在楚科奇人身上体现得最为明显。楚科奇人居住在西伯利亚东北部，他们使用的语言与美洲任何语言都无关。我的分析表明，由于美洲原住民的后裔回流到亚洲，楚科奇人拥有约40%的美洲原住民血统。^对于那些怀疑美洲原住民后裔是否可能从美洲重新扩张并对亚洲人口产生重大影响的人来说——他们习惯于认为亚洲和美洲之间的迁徙路径是单向的——他们或许会倾向于认为，楚科奇人与美洲原住民的基因亲缘关系仅仅反映了他们是亚洲美洲原住民的近亲。这种偏见也曾阻碍了我一年多的思考，当时我试图理解我们从不同美洲原住民群体中获得的数据。但基因数据表明，这种亲缘关系源于回迁，因为楚科奇人与某些完全由美洲原住民血统构成的人群的亲缘关系比与其他人群更为密切。这一发现只能解释为：美洲原住民的一个分支，其起源远晚于北美美洲原住民血统的最初分化，后来回迁到了亚洲。对此现象的解释是，定居在北美的爱斯基摩-阿留申语使用者与当地美洲原住民（贡献了他们约一半的血统）大量融合，然后将他们成功的生活方式带回北极，最终到达西伯利亚，这不仅影响了楚科奇人，也影响了当地爱斯基摩-阿留申语使用者。美洲原住民血统回流到亚洲的发现——这种发现很难用考古学证实——正是基因学独有的优势所在。

A second genetic revelation about Native American population history is clearest in the Chukchi, a population of far northeastern Siberia that speaks a language unrelated to any spoken in the Americas. My analyses revealed that the Chukchi harbor around 40 percent First American ancestry due to backflow from America to Asia.⁵⁰ For those who are dubious about the idea that descendants of First Americans could have reexpanded out of America and then made a substantial demographic impact on Asia—who are used to thinking about the migratory path between Asia and America as a one-way street—it might be tempting to argue that the genetic affinity of the Chukchi to Native Americans simply reflects that they are the closest cousins of the First Americans in Asia. This bias also impeded my own thinking for more than a year as I tried to make sense of the data we had from diverse Native Americans. But the genetic data clarify that the affinity is due to back-migration, as the Chukchi are more closely related to some populations of entirely First American ancestry than to others, a finding that can only be explained if a sublineage of First Americans that originated well after the initial diversification of First American lineages in North America migrated back to Asia. The explanation for this observation is that the Eskimo-Aleut speakers who established themselves in North America mixed heavily with local Native Americans (who contributed about half their ancestry) and then took their successful way of life back through the Arctic with them to Siberia, contributing not only to the Chukchi but also to local speakers of Eskimo-Aleut languages. The identification of a reflux of First American ancestry into Asia—a type of finding that is difficult to prove with archaeology—is the kind of surprise that genetics is in a unique position to deliver.

遗传学能提供的第三个例子是农业从墨西哥北部传入美国西南部的故事。如今，这些地区通过一个名为乌托语系的广泛分布的语系联系在一起。语言学家传统上认为阿兹特克语系是从北向南传播的，理由是该语系的大多数语言以及一些跨语系共享的植物名称都具有当今乌托-阿兹特克语系分布区北部地区的典型特征。然而，也有人认为这些语言是从墨西哥向北辐射传播的，与玉米种植的传播密切相关。考古学家彼得·贝尔伍德（Peter Bellwood）曾有力地提出，语言和人口往往会随着农业的传播而迁徙。⁵¹研究玉米传入该地区前后居民的古代DNA，并与现代居民进行比较，至少可以部分地验证这一理论。我们开始在古代DNA中发现一些线索。对古代玉米的研究表明，这种作物最初是在四千多年前通过一条高地路线（内陆，翻越丘陵）进入美国西南部，然后在大约两千年前被起源于低地沿海地区的玉米品种所取代。⁵²这是一个很好的例子，说明植物也拥有迁徙和反复混合的历史。虽然驯化作物的迁徙和混合可能更加剧烈，因为人类对作物进行了人工选择。我们很快就能检验新的人群是否随着新的作物而迁徙。

A third example of what genetics can offer is the story of the arrival of agriculture to the U.S. Southwest from northern Mexico. Today, these regions are linked by a widespread language family called Uto-Aztecan, which linguists have traditionally viewed as having spread from north to south, based on the fact that most of the languages in this group and some plant names that are shared across the languages are typical of the northern end of the present-day Uto-Aztecan distribution. However, others have argued that the languages radiated northward from Mexico, following the spread of maize agriculture. It has been suggested, most forcefully by the archaeologist Peter Bellwood, that languages and peoples tend to move with the spread of agriculture.⁵¹ Studying the ancient DNA of people who lived before and after the arrival of maize in the region, along with comparison to the present-day inhabitants, can test this theory at least in part. We are beginning to find some clues in ancient DNA. Studies of ancient maize have now shown that this crop first entered the U.S. Southwest by a highland route (inland, over hills) more than four thousand years ago, and then was replaced by strains of maize of a lowland coastal origin around two thousand years ago.⁵² This is a remarkable example of how plants, too, have had histories of migration and recurrent mixture, although in the case of domesticated crops the migrations and mixtures are if anything likely to be more dramatic because humans have subjected crops to artificial selection. It will only be a matter of time before we are able to test whether new peoples moved with the new crops.

当然，我们的梦想是更系统地开展此类研究。现代基因研究和古代DNA使我们能够发现美洲原住民文化如何通过迁徙联系在一起，以及语言和技术的传播如何与古代人口迁徙相对应。由于欧洲的剥削，美洲原住民人口及其文化遭受重创，许多这样的故事已经失传。基因学为我们重新发现这些失落的故事提供了契机，并有可能促进理解，甚至带来疗愈。

The dream, of course, is to carry out studies like these more systematically. Modern genetic studies and ancient DNA enable us to discover how Native American cultures are connected by links of migration, and how the spread of languages and technologies corresponded to ancient population movements. Many of these stories have been lost because of the European exploitation that has decimated Native American populations and their culture. Genetics offers the opportunity to rediscover lost stories, and has the potential to promote not just understanding but also healing.

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东亚人的基因组起源

The Genomic Origins of East Asians

南方路线的失败

The Failure of the Southern Route

东亚——涵盖中国、日本和东南亚的广袤区域——是人类进化的重要舞台之一。它拥有世界超过三分之一的人口，以及同样比例的语言多样性。陶器至少在一万九千年前就发明于此。 ¹一万五千年前，这里是美洲人类迁徙的起点。大约九千年前，东亚见证了农业的独立早期发展。

East Asia—the vast region encompassing China, Japan, and Southeast Asia—is one of the great theaters of human evolution. It harbors more than one third of the world’s population and a similar fraction of its language diversity. Pottery was first invented there at least nineteen thousand years ago.¹ It was the jumping-off point for the peopling of the Americas before fifteen thousand years ago. East Asia witnessed an independent and early invention of agriculture around nine thousand years ago.

东亚至少在约170万年前就已是人类的家园，这一时间与在中国发现的最古老的直立人骨骼的年代相符。 ²在印度尼西亚挖掘出的最早人类遗骸也同样古老。 ³ 古人类——他们的骨骼形态与大约30万年前在非洲化石记录中开始出现的具有现代解剖特征的人类不同 ⁴ ——自那时起就一直生活在东亚。例如，基因证据表明，丹尼索瓦人在5万年前不久就与现代澳大利亚人和新几内亚人的祖先发生了基因混合。考古和骨骼证据表明，身高约一米的“霍比特人”也在同一时期生活在印度尼西亚的弗洛勒斯岛。 ⁵

East Asia has been home to the human family for at least around 1.7 million years, the date of the oldest known Homo erectus skeleton found in China.² The earliest human remains excavated in Indonesia are similarly old.³ Archaic humans—whose skeletal form is not the same as that of humans whose anatomically modern features begin to appear in the African fossil record after around three hundred thousand years ago⁴—have lived in East Asia continuously since those times. For example, genetic evidence shows that the Denisovans mixed with ancestors of present-day Australians and New Guineans shortly after fifty thousand years ago. And archaeological and skeletal evidence shows that the one-meter-tall “Hobbits” also persisted until around this same time on Flores island in Indonesia.⁵

关于东亚古人类在多大程度上对现代人类的基因构成做出贡献，一直存在激烈的争论。如今，中西方遗传学家几乎一致认为，非洲以外的现代人类起源于大约五万年前的一次迁徙，这次迁徙在很大程度上取代了先前定居的人类群体。 ⁶另一方面，一些中国人类学家和考古学家记录了生活在东亚地区这一时期前后的人群在骨骼特征和石器风格上的相似之处，这引发了关于是否存在某种程度的延续性的疑问。 ⁷截至本文撰写之时，我们对东亚人口历史的了解与西欧亚大陆相比相对有限，因为已发表的古代DNA数据中只有不到5%来自东亚。这种差异反映了古代DNA技术起源于欧洲，而且由于政府的限制或倾向于由当地科学家主导研究，研究人员几乎不可能从中国和日本出口样本。这意味着这些地区错过了古代DNA革命的最初几年。

There has been intense debate about the extent to which the archaic humans of East Asia contributed genetically to people living today. Chinese and Western geneticists nearly all agree that present-day humans outside of Africa descend from a dispersal after around fifty thousand years ago, which largely displaced previously established human groups.⁶ Some Chinese anthropologists and archaeologists, on the other hand, have documented similarities in skeletal features and stone tool styles in people who lived in East Asia before and after this time, raising the question of whether there has been some degree of continuity.⁷ At the time of this writing, our knowledge of East Asian population history is relatively limited compared to that of West Eurasia because less than 5 percent of published ancient DNA data comes from East Asia. The difference reflects the fact that ancient DNA technology was invented in Europe, and it is nearly impossible for researchers to export samples from China and Japan because of government restrictions or a preference that studies be led by local scientists. This has meant that these regions have missed out on the first few years of the ancient DNA revolution.

在西方，主流叙事认为，大约五万年前，现代人类开始制造复杂的旧石器时代晚期石器，其特点是用预先准备好的石核，以全新的方式敲击出狭窄的石片。近东是已知最早发现旧石器时代晚期石器的地区，这项技术迅速传播到欧洲和欧亚大陆北部。鉴于旧石器时代晚期石器技术的创造者如此成功，人们自然会认为这项技术也应该传播到东亚。但事实并非如此。

In the west, the grand narrative is that sometime after around fifty thousand years ago, modern humans began making sophisticated Upper Paleolithic stone tools, which are characterized by narrow stone blades struck in a new way from pre-prepared cores. The Near East is the earliest known site of Upper Paleolithic stone tools, and this technology spread rapidly to Europe and northern Eurasia. It would be natural to expect, given how successful the people who made Upper Paleolithic technology were, that this know-how would have overspread East Asia too. But that is not what happened.

东方的考古模式与西方并不一致。大约四万年前，在中国和印度以东的广袤土地上，确实存在与现代人类到来相关的巨大行为变化的考古证据，包括使用精巧的骨制工具、贝壳珠或穿孔牙齿进行身体装饰，以及世界上已知最早的洞穴艺术。 ⁸在澳大利亚，人类营地的考古证据表明，现代人类至少在四万七千年前就已抵达那里， ⁹这与欧洲最早的现代人类证据的年代大致相同。 ¹⁰因此，现代人类抵达东亚和澳大利亚的时间与抵达欧洲的时间大致相同，这一点毋庸置疑。但是，令人费解的是，最早生活在中亚和东亚南部以及澳大利亚的现代人类并没有使用旧石器时代晚期的石器工具。相反，他们使用了其他技术，其中一些技术与数万年前非洲现代人类使用的技术更为相似。 ¹¹

The archaeological pattern in the east does not conform to that in the west. Around forty thousand years ago and across a vast tract of land in China and east of India there is indeed archaeological evidence of great behavioral change associated with the arrival of modern humans, including the use of sophisticated bone tools, shell beads or perforated teeth for body decoration, and the world’s earliest known cave art.⁸ In Australia, archaeological evidence of human campsites makes it clear that modern humans arrived there at least by about forty-seven thousand years ago,⁹ which is about as old as the earliest evidence for modern humans in Europe.¹⁰ So it is absolutely clear that modern humans arrived in East Asia and Australia around the same time as they came to Europe. But, puzzlingly, the first modern humans in central and southern East Asia, and those in Australia, did not use Upper Paleolithic stone tools. Instead, they used other technologies, some of which were more similar to those used by modern humans in Africa tens of thousands of years earlier.¹¹

受这些观察的启发，考古学家玛尔塔·米拉松·拉尔和罗伯特·弗利提出，澳大利亚最早的人类可能起源于现代人类在西方旧石器时代晚期技术发展之前，从非洲和近东迁徙而来的一次迁徙。根据这一“南方路线”假说，这些迁徙者早在五万年前就离开了非洲，沿着印度洋海岸线行进，他们的后裔如今生活在澳大利亚、新几内亚、菲律宾、马来西亚和安达曼群岛的土著居民中。 ¹²人类学家卡特琳娜·哈瓦蒂及其同事也记录了澳大利亚土著居民和非洲人之间的骨骼相似性，他们认为这为该假说提供了证据。 ¹³

Prompted by these observations, the archaeologists Marta Mirazon Lahr and Robert Foley argued that the first humans in Australia might derive from a migration of modern humans out of Africa and the Near East prior to the development of Upper Paleolithic technology in the west. According to this “Southern Route” hypothesis, the migrants left Africa well before fifty thousand years ago and skirted along the coast of the Indian Ocean, leaving descendants today among the indigenous people of Australia, New Guinea, the Philippines, Malaysia, and the Andaman Islands.¹² The anthropologist Katerina Harvati and colleagues also documented skeletal similarities between Australian Aborigines and Africans that, they argued, provide evidence for this model.¹³

南方路线假说远不止于声称早在五万年前非洲以外就存在现代人类——这一事实如今已被所有严肃的学者所接受。 ¹⁴五万年前非洲以外存在早期现代人类的证据包括在今以色列境内的斯库尔和卡夫泽发现的形态学上属于现代的骨骼，其年代可追溯到大约13万至10万年前。¹⁵在杰贝尔法亚遗址发现的距今约13万年的石器与同时期在东北非发现的石器相似，这表明现代人类早期就已跨越红海进入阿拉伯半岛。¹⁶此外，初步的遗传证据表明，现代人类早期就对非洲以外的地区产生了影响。尼安德特人的基因组中含有几个百分点的祖先成分，这些成分可能源于与现代人类谱系杂交。该谱系在几十万年前与现代人类谱系分离，这与斯库尔和卡夫泽遗址中可能存在的现代人类群体与尼安德特人祖先杂交的预期相符。17^虽然包括我在内的许多遗传学家仍在犹豫是否认为现代人类与尼安德特人早期杂交的发现具有说服力，但关键在于，几乎所有学者现在都认同现代人类早期曾向非洲以外地区扩散。亚洲的人类迁徙早于五万年前被广泛接受的、对当今所有非非洲裔人群产生重大影响的迁徙浪潮。南方路线假说提出的关键问题并非此类扩张是否发生过，而是它们是否对当今人类产生了重要的长期影响。

The Southern Route hypothesis was far more than a claim that there were modern humans outside of Africa well before fifty thousand years ago—a fact that every serious scholar now accepts.¹⁴ Evidence of early modern humans outside of Africa well before fifty thousand years ago includes the morphologically modern skeletons in Skhul and Qafzeh in present-day Israel that date to between around 130,000 to 100,000 years ago.¹⁵ Stone tools found at the site of Jebel Faya from around 130,000 years ago are similar to ones found in northeast Africa from around the same time, suggesting that modern humans made an early crossing of the Red Sea into Arabia.¹⁶ There is also tentative genetic evidence of an early impact of modern humans outside Africa, with Neanderthal genomes harboring a couple of percent of ancestry that may derive from interbreeding with a modern human lineage that separated a couple of hundred thousand years ago from present-day human lineages, as expected if a modern human population possibly related to that in Skhul and Qafzeh interbred with Neanderthal ancestors.¹⁷ Although many geneticists, including me, are still on the fence about whether this finding of earlier interbreeding between modern humans and Neanderthals is compelling, the key point is that almost all scholars now agree that there were early dispersals of modern humans into Asia that preceded the widely accepted dispersals after fifty thousand years ago that contributed in a major way to all present-day non-Africans. The outstanding question raised by the Southern Route hypothesis is not whether such expansions occurred, but whether they had an important long-term impact on humans living today.

2011年，埃斯克·威勒斯列夫（Eske Willerslev）领导的一项研究似乎表明，早期的扩张确实产生了影响。 ¹⁸他和他的同事报告了一项四群体检验，结果显示，欧洲人与东亚人共享的突变比与澳大利亚原住民共享的突变更多，这与南方路线对澳大利亚人谱系的贡献相符。他们将南方路线迁徙模型应用于基因组数据，估计澳大利亚原住民的祖先来自一个现代人类群体，该群体与现代欧洲人的分化时间是东亚祖先与欧洲人分化时间的两倍（7.5万至6.2万年前，而东亚祖先与欧洲人的分化时间为3.8万至2.5万年前）。

In 2011, Eske Willerslev led a study that seemed to show that the early expansions indeed left an impact.¹⁸ He and his colleagues reported a Four Population Test showing that Europeans share more mutations with East Asians than with Aboriginal Australians, as would be expected from a Southern Route contribution to the lineage of Australians. Applying a Southern Route migration model to the genomic data, they estimated that Australian Aborigines harbor ancestry from a modern human population that split from present-day Europeans at twice the time depth that East Asian ancestors split from Europeans (seventy-five thousand to sixty-two thousand years ago versus thirty-eight thousand to twenty-five thousand years ago).

然而，问题在于，该分析并未考虑澳大利亚人从古丹尼索瓦人那里继承的3%至6%的祖先成分。 ¹⁹由于丹尼索瓦人与现代人类的差异很大，他们的基因混合可能导致欧洲人与中国人共享的突变比与澳大利亚原住民共享的突变更多。事实上，这解释了研究结果。我的实验室表明，在考虑了丹尼索瓦人的基因混合后，欧洲人与中国人共享的突变并不比与澳大利亚人共享的突变更多，因此中国人和澳大利亚人几乎所有的祖先都来自一个同质群体，该群体的祖先更早地与欧洲人的祖先分离。²⁰这表明，非非洲人群历史上的一系列重大人口分裂发生在一个异常短的时间内——始于通往西欧亚人和东欧亚人的谱系的分离，终于澳大利亚原住民的祖先与许多东欧亚大陆居民的祖先的分离。这些人口分裂都发生在尼安德特人与非非洲人祖先杂交之后（距今约5.4万至4.9万年前），以及丹尼索瓦人与澳大利亚人祖先混合之前。据基因估计，丹尼索瓦人与澳大利亚人祖先混合的时间比尼安德特人/现代人混合的时间晚12%，即距今约4.9万至4.4万年前。 ²¹

There was a problem, though, which is that the analysis did not account for the 3 to 6 percent of ancestry that Australians inherited from archaic Denisovans.¹⁹ Because Denisovans were so divergent from modern humans, mixture from them could cause Europeans to share more mutations with Chinese than with Australian Aborigines. Indeed, this explained the findings. My laboratory showed that after accounting for Denisovan mixture, Europeans do not share more mutations with Chinese than with Australians, and so Chinese and Australians derive almost all their ancestry from a homogeneous population whose ancestors separated earlier from the ancestors of Europeans.²⁰ This revealed that a series of major population splits in the history of non-Africans occurred in an exceptionally short time span—beginning with the separation of the lineages leading to West Eurasians and East Eurasians, and ending with the split of the ancestors of Australian Aborigines from the ancestors of many mainland East Eurasians. These population splits all occurred after the time when Neanderthals interbred with the ancestors of non-Africans fifty-four to forty-nine thousand years ago, and before the time when Denisovans and the ancestors of Australians mixed, genetically estimated to be 12 percent more recent than the Neanderthal/modern human admixture, that is, forty-nine to forty-four thousand years ago.²¹

在尼安德特人和丹尼索瓦人与现代人类杂交的相对较短的时间间隔内，谱系分离的快速发生表明，在整个欧亚大陆，现代人类不断迁徙到新的环境中，凭借其技术或生活方式得以扩张，从而取代了先前居住在那里的人群。这种扩张速度如此之快，以至于很难想象那些已经在那里居住了近两百万年的古人类——根据与丹尼索瓦人杂交的证据，我们知道在现代人类扩张时，他们也生活在那里——会进行多少抵抗。即使早期现代人类是通过南方路线扩张到东亚的，他们也可能被后来的人类迁徙浪潮所取代，因此可以排除他们对现代人类祖先的贡献超过极小比例的可能性。22^在东亚和西亚，现代人类从非洲和近东的扩张就像擦掉黑板一样，为新人群创造了一张白纸。欧亚大陆的古老人口消亡后，新的群体迅速占据了这片土地。目前尚无任何遗传证据表明，现代东亚人拥有来自这些早期人口的显著祖先血统^。23

The rapid succession of lineage separations during the relatively short interval between Neanderthal and Denisovan interbreeding with modern humans suggests that throughout Eurasia, modern humans were moving into new environments where their technology or lifestyle allowed them to expand, displacing the previously resident groups. The spread was so fast that it is hard to imagine that archaic humans who had already been resident there for close to two million years, and who we know were also there when modern humans expanded based on the evidence of interbreeding with Denisovans, put up much resistance. Even if early modern humans expanded into East Asia via a Southern Route, they were likely also replaced by later waves of human migrants and can be ruled out as having contributed more than a very small percentage of the ancestry of present-day people.²² In East Asia as in West Eurasia, the expansion of modern humans out of Africa and the Near East had an effect akin to the erasing of a blackboard, creating a blank slate for the new people. The old populations of Eurasia collapsed, and in their place came new groups that swiftly inhabited the landscape. There is no genetic evidence of any substantial ancestry from these earlier populations in present East Asians.²³

因此，如果今天东亚和澳大利亚几乎所有现代人类的祖先都源自于对西方文明做出贡献的同一群体。欧亚大陆的人们，是什么原因导致东南亚人和澳大利亚人错过了与现代人类向近东和欧洲扩散密切相关的旧石器时代晚期技术？

So if essentially all modern human ancestry in East Asia and Australia today derives from the same group that contributed to West Eurasians, what explains how Southeast Asians and Australians missed out on the Upper Paleolithic technology that is so tightly linked with the spread of modern human populations into the Near East and Europe?

考古记录中最早出现的、具有旧石器时代晚期特征的长刃石器可追溯到五万至四万六千年前。 ²⁴但从基因角度来看，通往西欧亚人和东亚人的谱系分化可能更为古老，因为正如我之前讨论过的，这种分化几乎可以肯定发生在现代人类与尼安德特人混合之后的几千年内，而尼安德特人混合发生在五万四千年至四万九千年前。因此，西欧亚人和东亚人祖先的主要分化可能发生在旧石器时代晚期技术发展之前，而这项技术的地理分布可能仅仅反映了发明它的人群的分布范围。

The first long-bladed stone tools characteristic of Upper Paleolithic technology in the archaeological record date to between fifty thousand and forty-six thousand years ago.²⁴ But genetically, the split of the lineages leading to West Eurasians and East Asians may have been more ancient since, as I have discussed, it almost certainly occurred within a few thousand years after the admixture of modern humans with Neanderthals fifty-four thousand to forty-nine thousand years ago. So the main split of West Eurasian and East Asian ancestors could have occurred before the development of Upper Paleolithic technology, and the geographic distribution of this technology could just reflect the spread of the population that invented it.

有一项佐证理论认为，旧石器时代晚期技术是在通往西欧亚人和东亚人的主要谱系分化之后发展起来的。已知最早的古代北欧亚人，其化石发现于西伯利亚东部马尔塔遗址，距今约24000年，属于通往西欧亚人的^谱系。这一直令遗传学家感到困惑，因为古代北欧亚人在地理位置上更靠近东亚。但考虑到旧石器时代晚期石器的地理分布，这一解释就说得通了。这些石器不仅与西欧亚人有关，也与北欧亚人和东北亚人有关。如果旧石器时代晚期技术在一个人群中发展成熟，而这个人群生活在通往古代北欧亚人和西欧亚人的谱系分化之前，但在通往东亚人的谱系分化之后，那么石器技术和遗传祖先的分布都符合预期。

There is a piece of corroborating evidence for the theory that Upper Paleolithic technology developed after the split of the main lineages leading to West Eurasians and East Asians. The Ancient North Eurasians, known earliest from the approximately twenty-four-thousand-year-old remains of the boy from the Mal’ta site in eastern Siberia,²⁵ are on the lineage leading to West Eurasians, which has always been puzzling for geneticists because the Ancient North Eurasians lived geographically closer to East Asia. But it makes sense in light of the geographic distribution of Upper Paleolithic stone tools, which are associated not just with West Eurasians but also North Eurasians and Northeast Asians. Both the distributions of stone tool technology and of genetic ancestry are as expected if Upper Paleolithic technology came into full flower in a population that lived prior to the separation of the lineages leading to Ancient North Eurasians and West Eurasians, but after the separation of the lineage leading to East Asians.

无论旧石器时代晚期技术未能传播到东南亚南部的原因是什么，从之后发生的事情，以及这些人成功驱逐了丹尼索瓦人等先前居住在那里的居民，可以清楚地看出，旧石器时代晚期技术本身并非现代人类在大约五万年前之后成功迁徙到欧亚大陆的必要条件。真正起作用的远不止旧石器时代晚期的石器工具。技术——这种创造力和适应能力（技术只是这种创造力和适应能力的体现）使得不断扩张的现代人类得以在世界各地，包括东方，取得胜利。

Whatever the reason for the fact that Upper Paleolithic technology never spread to southern East Asia, it is clear from what happened next, and the success these people had in displacing the previously resident populations such as Denisovans, that Upper Paleolithic technology itself was not essential to the successful spread of modern humans into Eurasia after around fifty thousand years ago. It was something more profound than Upper Paleolithic stone tool technology—an inventiveness and adaptability of which the technology was just a manifestation—that allowed these expanding modern humans to prevail everywhere, including in the east.

现代东亚的开端

The Beginnings of Modern East Asia

2009年发表了首个针对现代东亚人群的基因组调查，报告了来自近75个群体的近2000名个体的数据。 ²⁶作者重点关注了他们的发现：东南亚的人类多样性高于东北亚。他们将这种模式解释为现代人类曾以单一浪潮抵达东南亚，然后从那里向北扩散到中国及更远地区的证据。他们遵循一种模型，该模型认为，当今人群的遗传多样性可以归因于一个单一人群从非洲迁徙并向各个方向扩散，随着每个小型先驱群体的分化而逐渐丧失遗传多样性。 ²⁷但我们现在知道，这种模型可能适用范围有限。在欧洲，人口经历了多次更替和深度混合，我们现在从古代DNA中得知，西欧亚大陆目前的遗传多样性模式扭曲了现代人类首次迁徙到该地区的真实情况。 ²⁸这种从南向北迁徙，并在途中逐渐丧失多样性的模型，对于东亚而言是完全错误的。

The first genomic survey of modern East Asian populations was published in 2009, and reported data on nearly two thousand individuals from almost seventy-five populations.²⁶ The authors focused on their finding that human diversity is greater in Southeast Asia than in Northeast Asia. They interpreted this pattern as evidence of a single wave of modern humans reaching Southeast Asia and then spreading from there northward into China and beyond, following a model in which the genetic diversity of present-day populations can be accounted for by a single population moving out of Africa and spreading in all directions, losing genetic diversity as each small pioneer group budded off.²⁷ But we now know that this model is likely to be of limited use. In Europe there have been multiple population replacements and deep mixtures, and we now know from ancient DNA that present-day patterns of diversity in West Eurasia provide a distorted picture of the first modern human migrations into the region.²⁸ The model of a south-to-north migration, losing diversity along the way, is profoundly wrong for East Asia.

2015年，王传超来到我的实验室，带来了一份珍贵的资料：来自约40个不同中国人群的约400名现代个体的全基因组数据。由于生物材料出口受到限制，中国在DNA研究中的样本量一直很稀少。因此，王传超和他的同事在中国完成了遗传学研究，并通过电子方式将数据带给了我们。在接下来的18个月里，我们分析了这些数据，并结合之前发表的来自其他东亚国家的数据，以及我们实验室生成的来自俄罗斯远东地区的古代DNA。这使我们能够对东亚深远的人口历史及其现代居民的起源获得新的遗传学见解^。29

In 2015 Chuanchao Wang arrived in my laboratory bearing a treasure: genome-wide data from about four hundred present-day individuals from about forty diverse Chinese populations. China had been sparsely sampled in DNA studies because of regulations limiting the export of biological material. Wang and his colleagues therefore did the genetic work in China, and he brought the data to us electronically. Over the next year and a half, we analyzed these data together with more data from other East Asian countries that had previously been published and with ancient DNA from the Russian Far East generated in our lab. This allowed us to come up with new genetic insights about the deep population history of East Asia and the origins of its current inhabitants.²⁹

通过主成分分析，我们发现祖先当今绝大多数东亚人的特征可以归纳为三个群体。

By using a principal component analysis, we found that the ancestry of the great majority of East Asians living today can be described by three clusters.

第一个聚类中心人群是目前居住在中国东北与俄罗斯交界处的黑龙江流域的人们。它包含了我的实验室和其他实验室从黑龙江流域获得的古代DNA数据。因此，该地区已有超过八千年的遗传相似人群居住^。30

The first cluster is centered on people currently living in the Amur River basin on the boundary between northeastern China and Russia. It includes ancient DNA data that my laboratory and others had obtained from the Amur River basin. So, this region has been inhabited by genetically similar populations for more than eight thousand years.³⁰

第二个集群位于青藏高原，这是一片位于喜马拉雅山脉以北的广阔区域，其中大部分地区的海拔比欧洲阿尔卑斯山脉的最高峰还要高。

The second cluster is located on the Tibetan Plateau, a vast area north of the Himalayas, much of which is at a higher altitude than the tallest of the European Alps.

第三个集群以东南亚为中心，主要由居住在中国大陆沿海海南岛和台湾岛的土著居民组成。

The third cluster is centered in Southeast Asia, and is most strongly represented by individuals from indigenous populations living on the islands of Hainan and Taiwan off the coast of mainland China.

我们运用四群体检验统计量来评估代表这些群体的现代人群与美洲原住民、安达曼群岛居民和新几内亚人之间可能存在的关联模型。后三个群体至少自上次冰河时代以来就与东亚大陆的祖先基本隔离，他们与东亚相关的祖先成分实际上可以作为那个时期的古代DNA。

We used Four Population Test statistics to evaluate models of the possible relationships among present-day populations representing these clusters and Native Americans, Andaman islanders, and New Guineans. The latter three populations have been largely isolated from the ancestors of mainland East Asians at least since the last ice age, and their East Asian–related ancestry effectively serves as ancient DNA from that period.

我们的分析支持这样一种人口历史模型：如今生活在东亚大陆的绝大多数现代人类祖先主要来源于两个远古时期就已分离的谱系以不同比例混合而成。这两个谱系的成员向四面八方扩散，他们彼此之间以及与他们遇到的其他一些人群的融合，改变了东亚的人类格局。

Our analysis supported a model of population history in which the modern human ancestry of the great majority of mainland East Asians living today derives largely from mixtures—in different proportions—of two lineages that separated very anciently. Members of these two lineages spread in all directions, and their mixture with each other and with some of the populations they encountered transformed the human landscape of East Asia.

长江和黄河流域的幽灵人口

The Ghost Populations of the Yangtze and Yellow Rivers

世界上少数几个独立发展农业的国家之一就是中国。考古证据表明，大约九千年前，农民就开始耕种风力资源。在中国北方黄河附近的冲积沙土上，人们开始种植小米和其他作物。大约在同一时期，在南方长江流域，另一群农民也开始种植其他作物，包括水稻。 ³¹长江流域的农业沿着两条路线扩张——一条陆路路线，大约在五千年前延伸至越南和泰国；另一条海路路线，大约在同一时期到达台湾岛。在印度和中亚，中国农业首次与来自近东的农业扩张发生碰撞。语言模式也暗示了人口迁徙的可能性。如今，东亚大陆的语言至少包含十一个主要语系：汉藏语系、台卡岱语系、南岛语系、南亚语系、苗瑶语系、日语系、印欧语系、蒙古语系、突厥语系、通古斯语系和朝鲜语系。彼得·贝尔伍德认为，前六个语系与东亚农业人口的扩张相对应，他们在迁徙过程中传播了他们的语言。 ³²

One of the handful of places in the world where farming independently began was China. Archaeological evidence shows that starting around nine thousand years ago, farmers started tilling the windblown sediments near the Yellow River in northern China, growing millet and other crops. Around the same time, in the south near the Yangtze River, a different group of farmers began growing other crops, including rice.³¹ Yangtze River agriculture expanded along two routes—a land route that reached Vietnam and Thailand beginning around five thousand years ago, and a maritime route that reached the island of Taiwan around the same time. In India and in central Asia, Chinese agriculture collided for the first time with the expansion of agriculture from the Near East. Language patterns also hint at the possibility of movements of people. Today the languages of mainland East Asia comprise at least eleven major families: Sino-Tibetan, Tai-Kadai, Austronesian, Austroasiatic, Hmong-Mien, Japonic, Indo-European, Mongolic, Turkic, Tungusic, and Koreanic. Peter Bellwood has argued that the first six correspond to expansions of East Asian agriculturalists disseminating their languages as they moved.³²

我们能从遗传学角度得出什么结论呢？由于中国对骨骼材料出口的限制，目前遗传数据所提供的关于东亚早期人口历史的信息远远落后于西欧亚大陆甚至美洲。尽管如此，王教授还是根据我们掌握的少量古代DNA数据以及现代人群的变异模式，尽可能地了解了一些情况。

What can we say based on the genetics? Because of restrictions on exporting skeletal material from China, the information that genetic data currently provide about the deep population history of East Asia is far behind that of West Eurasia or even of America. Nevertheless, Wang learned what he could based on the little ancient DNA data we had and patterns of variation in present-day people.

我们发现，在东南亚和台湾，许多人群的大部分或全部祖先都源自一个同质的祖先群体。由于这些人群的分布区域与长江流域水稻种植业扩张的区域高度重合，因此我们很容易推测他们是水稻种植业发展者的后裔。我们目前还没有长江流域早期农民的古代DNA，但我猜测他们的DNA与我们重建的“长江幽灵人群”（我们给构成现代东南亚人绝大部分祖先的人群起的名字）相符。

We found that in Southeast Asia and Taiwan, there are many populations that derive most or all of their ancestry from a homogeneous ancestral population. Since the locations of these populations strongly overlap with the regions where rice farming expanded from the Yangtze River valley, it is tempting to hypothesize that they descend from the people who developed rice agriculture. We do not yet have ancient DNA from the first farmers of the Yangtze River valley, but my guess is that they will match this reconstructed “Yangtze River Ghost Population,” the name that we have given the population that contributed the overwhelming majority of ancestry to present-day Southeast Asians.

但我们发现，汉族——世界上人口最多的族群，人口普查数据超过12亿——并非直接起源于长江幽灵族。相反，汉族还拥有很大比例来自另一个与长江幽灵族群差异极大的东亚族群的血统。其中比例最高的是……在北方汉族人中发现了其他祖先成分，这与2009年以来的研究结果相符，这些研究表明汉族人存在从北到南的细微差异。 ³³这种模式符合汉族祖先从北方向外辐射并在向南扩散的过程中与当地居民融合的历史预期。 ³⁴

But we found that the Han Chinese—the world’s largest group with a census size of more than 1.2 billion—is not consistent with descending directly from the Yangtze River Ghost population. Instead, the Han also have a large proportion of ancestry from another deeply divergent East Asian lineage. The highest proportions of this other ancestry are found in northern Han, consistent with work since 2009 that has shown that the Han harbor subtle differences along a north-to-south gradient.³³ This pattern is as expected from a history in which the ancestors of the Han radiated out from the north and mixed with locals as they spread south.³⁴

另一种祖先类型会是什么呢？根据历史记载，公元前202年统一中国的汉族被认为是由更早的华夏部落演变而来，而华夏部落又起源于中国北方黄河流域更早的族群。黄河流域是中国两大农业发源地之一，也是大约3600年前农业传播到青藏高原东部的源头。^由于汉族和藏族都属于汉藏语系，我们不禁思考他们是否也可能拥有某种独特的祖先类型。

What could the other ancestry type be? The Han, who unified China in 202 BCE, are believed based on historical sources to have emerged from the earlier Huaxia tribes who themselves emanated from earlier groups in the Yellow River Valley of northern China. This was one of the two Chinese regions where farming originated, and it is also the place from which farming spread to the eastern Tibetan Plateau beginning around thirty-six hundred years ago.³⁵ Since the Han and Tibetans are also linked by their Sino-Tibetan languages, we wondered whether they might share a distinctive type of ancestry as well.

王教授构建东亚人口深层历史模型时发现，汉族和藏族都拥有大量来自一个如今已不复存在的单一族群的血统，而这个族群也并非东南亚许多族群的祖先。基于考古、语言和遗传学的综合证据，我们将此族群称为“黄河幽灵族群”，并推测其在北方发展农业的同时传播了汉藏语系。黄河流域早期农民的古DNA将揭示这一推测是否正确。一旦获得古DNA，我们还能了解东亚人口历史中一些仅凭分析当今人群无法辨识的特征，因为当今人群的深层历史已被多层迁徙和混血所掩盖。

When Wang built his model of deep East Asian population history, he found that the Han and Tibetans both harbored large proportions of their ancestry from a population that no longer exists in unmixed form and that we could exclude as having contributed ancestry to many Southeast Asian populations. Because of the combined evidence of archaeology, language, and genetics, we called this the “Yellow River Ghost Population,” hypothesizing that it developed agriculture in the north while spreading Sino-Tibetan languages. Ancient DNA from the first farmers of the Yellow River Valley will reveal whether this conjecture is correct. Once available, ancient DNA will also make it possible to learn about features of East Asian population history that are impossible to discern based on analysis only of populations living today, whose deep history has been clouded by many additional layers of migration and mixture.

东亚边缘地区的大混血

The Great Admixtures at the East Asian Periphery

中国平原的核心农业人口——长江和黄河沿岸的“幽灵人口”——形成后，便向各个方向扩张，与几千年前到达的人群融合。

Once the core agricultural populations of the Chinese plain—the Yangtze and Yellow River ghost populations—formed, they expanded in all directions, mixing with groups that had arrived in earlier millennia.

青藏高原的居民——他们约有三分之二的祖先来自与汉族有血缘关系的黄河幽灵族群——便是这种扩张的一个例证。他们很可能是最早将农业带到该地区的民族，同时他们约有三分之一的祖先来自东亚早期的一个分支，这个分支很可能与西藏的土著狩猎采集者相对应。 ³⁶

The peoples of the Tibetan Plateau—who harbor a mixture of about two-thirds of their ancestry from the same Yellow River ghost population that contributed to the Han—are one example of this expansion. They likely brought farming for the first time to the region, as well as about one-third of their ancestry from an early branch of East Asians that plausibly corresponds to Tibet’s indigenous hunter-gatherers.³⁶

另一个例子是日本人。数万年来，日本列岛一直以狩猎采集为生，但大约在2300年前，源自大陆的农业开始兴起，并与一种与朝鲜半岛当代文化有着明显相似之处的考古文化相关联。基因数据证实，农业向岛屿的传播是通过人口迁徙实现的。斋藤成也及其同事将现代日本人建模为两个起源于东亚、但古代分化的人群的混合体——一个与现代韩国人有关，另一个与如今仅分布于日本最北端岛屿的阿伊努人有关，他们的DNA与农业出现之前的狩猎采集者的DNA相似 ³⁷ ——据此估计，现代日本人约有80%的农民血统和20%的狩猎采集者血统。根据当代日本人中与农民相关的祖先成分比例，我们和斋藤估计，混血的平均时间约为1600年前。 ³⁸这个时间远晚于农民首次抵达该地区的时间，表明在农民抵达之后，狩猎采集者和农民之间的社会隔离可能需要数百年时间才能瓦解。这一时间与古墳时代相吻合，古墳时代是日本许多岛屿首次统一于同一统治之下的时期，这或许标志着如今日本大部分地区呈现出的同质性特征的开端。

Another example is the Japanese. For many tens of thousands of years, the Japanese archipelago was dominated by hunter-gatherers, but after around twenty-three hundred years ago, mainland-derived agriculture began to be practiced and was associated with an archaeological culture with clear similarities to contemporary cultures on the Korean peninsula. The genetic data confirm that the spread of farming to the islands was mediated by migration. Modeling present-day Japanese as a mixture of two anciently divergent populations of entirely East Asian origin—one related to present-day Koreans and one related to the Ainu who today are restricted to the northernmost Japanese island and whose DNA is similar to that of pre-farming hunter-gatherers³⁷—Naruya Saitou and colleagues estimated that present-day Japanese have about 80 percent farmer and 20 percent hunter-gatherer ancestry. Relying on the sizes of segments of farmer-related ancestry in present-day Japanese, we and Saitou estimated the average date of mixture to be around sixteen hundred years ago.³⁸ This date is far later than the first arrival of farmers to the region and suggests that after their arrival, it may have taken hundreds of years for social segregation between hunter-gatherers and farmers to break down. The date corresponds to the Kofun period, the first time when many Japanese islands were united under a single rule, perhaps marking the beginnings of the homogeneity that characterizes much of Japan today.

古DNA也揭示了东南亚大陆人类的悠久历史。2017年，我的实验室从越南曼巴克遗址（距今近四千年）的古代人类遗骸中提取了DNA。在那里，骨骼形状与如今长江流域农业居民和东亚人相似的人类，与骨骼形状更接近于早期居住于此的狩猎采集者的人类遗骸并排埋葬。39马克^·利普森我的实验室研究表明，在古代越南，我们分析的所有样本都是东欧亚人早期分化谱系和长江幽灵人群的混合体，其中一些曼巴克农民样本中长江幽灵人群的比例高于其他样本。曼巴克农民的主要群体也具有来自这两个谱系的祖先比例，与当今使用孤立的南亚语系语言的人群相似。这些发现与南亚语系语言是由来自中国南方的稻农迁徙并与当地狩猎采集者通婚而传播的理论相符。^即使在今天，柬埔寨和越南的大量南亚语系语言使用者仍然保留着相当比例的狩猎采集者祖先血统。

Ancient DNA is also revealing the deep history of humans in mainland Southeast Asia. In 2017, my laboratory extracted DNA from ancient humans at the almost four-thousand-year-old site of Man Bac in Vietnam, where people with skeletons similar in shape to those of Yangtze River agriculturalists and East Asians today were buried side by side with individuals with skeletons more similar to those of the previously resident hunter-gatherers.³⁹ Mark Lipson in my laboratory showed that in ancient Vietnam, all the samples we analyzed were a mixture of an early splitting lineage of East Eurasians and the Yangtze River Ghost Population, with the proportion of the Yangtze River Ghost Population higher in some of the Man Bac farmers we analyzed than in others. The main group of Man Bac farmers also had proportions of ancestry from these two lineages that were similar to those seen in present-day speakers of isolated Austroasiatic languages. These findings are consistent with the theory that Austroasiatic languages were spread by a movement of rice farmers from southern China who interbred with local hunter-gatherers.⁴⁰ Even today, large Austroasiatic-speaking populations in Cambodia and Vietnam harbor substantial albeit smaller proportions of this hunter-gatherer ancestry.

人口扩散带来的遗传影响，以及南亚语系语言的传播，其影响范围远超这些语言如今的分布区域。在另一项研究中，利普森（Lipson）指出，在南岛语系占主导地位的印度尼西亚西部，相当一部分人的祖先来自与大陆部分南亚语系使用者拥有相同谱系的人群。 ⁴¹利普森的发现表明，南亚语系使用者可能最先抵达印度尼西亚西部，随后是祖先构成截然不同的南岛语系使用者。这或许可以解释语言学家亚历山大·阿德拉尔（Alexander Adelaar）和罗杰·布伦奇（Roger Blench）为何注意到婆罗洲岛上使用的南岛语系语言中存在南亚语系借词（源自其他语系的词汇）。 ⁴²另一种解释是，如果南岛语系农民绕道大陆，与当地的南亚语系使用者融合，然后再进一步扩散到印度尼西亚西部，利普森的发现也可以得到印证。

The genetic impact of the population spread that also dispersed Austroasiatic languages went beyond places where these languages are spoken today. In another study, Lipson showed that in western Indonesia where Austronesian languages are predominant, a substantial share of the ancestry comes from a population that derives from the same lineages as some Austroasiatic speakers on the mainland.⁴¹ Lipson’s discovery suggested that Austroasiatic speakers may have come first to western Indonesia, followed by Austronesian speakers with very different ancestry. This might explain why linguists Alexander Adelaar and Roger Blench noticed the presence of Austroasiatic loan words (words with an origin in another language group) in the Austronesian languages spoken on the island of Borneo.⁴² Alternatively, Lipson’s findings could be explained if Austronesian-speaking farmers took a detour through the mainland, mixing with local Austroasiatic-speaking populations there before spreading farther to western Indonesia.

东亚核心地区农民向边缘地区迁徙的最显著例证莫过于南岛语系的扩张。如今，南岛语系分布于包括数百个偏远太平洋岛屿在内的广袤区域。考古学、语言学和遗传学的综合数据表明，大约五千年前，东亚大陆的农业传播到了台湾，而台湾正是南岛语系最古老的分支所在地。这些农民随后向南迁徙至菲律宾。大约四千年前，他们向南迁徙，绕过新几内亚岛及其东部的小岛。 ⁴³大约在他们从台湾迁徙的同时，他们可能发明了舷外支架独木舟，这种船的两侧用原木支撑，可以增加在波涛汹涌的海面上的稳定性，使他们能够在公海航行。三千三百年后，一种名为拉皮塔（Lapita）的陶器制作工艺出现在新几内亚岛以东，此后不久，他们开始进一步向太平洋扩张，迅速到达距离新几内亚岛三千公里的瓦努阿图。仅仅几百年后，他们就扩散到包括汤加和萨摩亚在内的西波利尼西亚群岛，然后在经历了大约一千二百年的漫长停滞期后，在八百年前，他们扩散到太平洋上最后几个适宜居住的岛屿——新西兰、夏威夷和复活节岛。南岛语系向西扩张同样令人瞩目，至少在1300年前就已抵达非洲沿岸的马达加斯加，位于菲律宾以西9000公里处，这也解释了为什么如今几乎所有的印度尼西亚人以及马达加斯加人都讲南岛语系语言^。44

The most impressive example of the movements of farmers from the East Asian heartland to the periphery is the Austronesian expansion. Today, Austronesian languages are spread across a vast region including hundreds of remote Pacific islands. Archaeological, linguistic, and genetic data taken together have suggested that around five thousand years ago, mainland East Asian farming spread to Taiwan, where the deepest branches of the Austronesian language family are found. These farmers spread southward to the Philippines about four thousand years ago, and farther south around the large island of New Guinea and into the smaller islands to its east.⁴³ At about the time they spread from Taiwan they probably invented outrigger canoes, boats with logs propped on the side that increase their stability in rough waters, making it possible to navigate the open seas. After thirty-three hundred years ago, ancient peoples making pottery in a style called Lapita appeared just to the east of New Guinea and soon afterward started expanding farther into the Pacific, quickly reaching Vanuatu three thousand kilometers from New Guinea. It took only a few hundred more years for them to spread through the western Polynesian islands including Tonga and Samoa, and then, after a long pause lasting until around twelve hundred years ago, they spread to the last habitable Pacific islands of New Zealand, Hawaii, and Easter Island by eight hundred years ago. The Austronesian expansion to the west was equally impressive, reaching Madagascar off the coast of Africa nine thousand kilometers to the west of the Philippines at least thirteen hundred years ago, and explaining why almost all Indonesians today as well as people from Madagascar speak Austronesian languages.⁴⁴

我实验室的马克·利普森（Mark Lipson）发现了一种用于追踪南岛语系扩张的遗传示踪染料——这种血统几乎存在于所有使用南岛语系语言的人群中。利普森发现，几乎所有使用这些语言的人都至少拥有一部分来自一个与台湾原住民关系更为密切的人群的血统，而非与任何东亚大陆人群的关系。这支持了南岛语系从台湾地区扩张的理论。 ⁴⁵

Mark Lipson in my laboratory identified a genetic tracer dye for the Austronesian expansion—a type of ancestry that is nearly always present in peoples who today speak Austronesian languages. Lipson found that nearly all people who speak these languages harbor at least part of their ancestry from a population that is more closely related to aboriginal Taiwanese than it is to any mainland East Asian population. This supports the theory of an expansion from the region of Taiwan.⁴⁵

尽管基因、语言和考古学上的共同线索为南岛语系的扩张提供了令人信服的证据，但一些遗传学家对拉皮塔人迁徙期间最早定居于西南太平洋偏远岛屿的人类是来自台湾农民的纯血统后裔这一观点持怀疑态度。 ⁴⁶ 这些移民怎么可能在几乎没有与当地居民融合的情况下，穿越巴布亚新几内亚这片已有四万多年历史的地区呢？鉴于如今巴布亚新几内亚以东的所有太平洋岛民都至少拥有25%的巴布亚血统，这种情况似乎不太可能。高达 90% 左右^。47这如何与当时盛行的假设相吻合呢？即拉皮塔考古文化是在最终起源于中国农业中心（经由台湾）的人们与新几内亚人之间密切交流的时期形成的？

Although there are genetic, linguistic, and archaeological common threads that make a compelling case for the Austronesian expansion, some geneticists balked at the suggestion that the first humans who peopled the remote islands of the Southwest Pacific during the Lapita dispersal were unmixed descendants of farmers from Taiwan.⁴⁶ How could these migrants have passed over the region of Papua New Guinea, occupied for more than forty thousand years, while mixing little with its inhabitants? Such a scenario seemed improbable in light of the fact that today, all Pacific islanders east of Papua New Guinea have at least 25 percent Papuan ancestry and up to around 90 percent.⁴⁷ How could this fit with the prevailing hypothesis that the Lapita archaeological culture was forged during a period of intense exchange between people ultimately originating in the farming center of China (via Taiwan) and New Guineans?

2016年，古DNA再次带来突破，推翻了此前遗传学文献中盛行的观点。在南太平洋等热带气候地区，保存完好的古DNA很难找到。但正如前文所述，当罗恩·平哈西及其同事发现，颅骨致密的岩骨（包含内耳结构）中的DNA含量有时比其他骨骼通常保存的DNA含量高出百倍时，从太平洋地区获取可用DNA的可能性发生了改变。 ⁴⁸我们最初在研究太平洋地区的样本时遇到了困难，但当我们尝试研究岩骨时，情况发生了转变。 ⁴⁹

In 2016, ancient DNA struck again, disproving the view that had prevailed until then in the genetic literature. Well-preserved ancient DNA is hard to find in tropical climates like those of the southern Pacific. But the ability to get working DNA from the Pacific changed when, as described earlier, Ron Pinhasi and colleagues showed that DNA from the dense petrous bone of the skull containing the structures of the inner ear sometimes preserves up to one hundred times more DNA than can typically be obtained from other bones.⁴⁸ We initially struggled to study samples from the Pacific, but when we tried petrous bones, our luck changed.⁴⁹

我们成功地从生活在约三千年前至两千五百年前的瓦努阿图和汤加的拉皮塔陶器文化相关的古代居民身上提取了DNA。我们发现，他们不仅没有大量的巴布亚血统，反而几乎没有。 ⁵⁰这表明，后来一定发生了一次从新几内亚地区向遥远的太平洋地区的大规模迁徙。这次迁徙至少始于两千四百年前，因为我们分析的所有来自那时及之后的瓦努阿图样本都至少含有90%的巴布亚血统。⁵¹后来的这波迁徙是如何如此彻底地取代了拉皮塔陶器原住民的后裔，同时又保留了他们可能使用的语言，至今仍是一个谜。但基因数据表明，事实的确如此。这种结果只有基因学才能提供——确凿地证明了大规模人口迁徙的发生。这一证明不同民族之间存在互动的证据，又把解释这些迁徙的性质和影响的任务交到了考古学家手中。

We succeeded at getting DNA from ancient people associated with the Lapita pottery culture in the Pacific islands of Vanuatu and Tonga who lived from around three thousand to twenty-five hundred years ago. Far from having substantial proportions of Papuan ancestry, we found that in fact they had little or none.⁵⁰ This showed that there must have been a later major migration from the New Guinea region into the remote Pacific. The late migration must have begun by at least twenty-four hundred years ago, as all the Vanuatu samples we have analyzed from that time and afterward had at least 90 percent Papuan ancestry.⁵¹ How this later wave could have so comprehensively replaced the descendants of the original people who made Lapita pottery and yet retained the languages these people probably spoke remains a mystery. But the genetic data show that this is what happened. This is the kind of result that only genetics can deliver—the definitive documentation that major movements of people occurred. This proof of interaction between highly divergent peoples puts the ball back into the court of archaeologists to explain the nature and effects of those migrations.

来自西南太平洋的古代DNA研究不断带来意想不到的发现。当我们和约翰内斯·克劳斯（Johannes Krause）的实验室分别独立分析瓦努阿图的巴布亚人祖先时，我们发现它与目前生活在新几内亚附近俾斯麦群岛的人群的祖先关系更为密切，而不是与……尽管所罗门群岛位于通往瓦努阿图的航线上，但目前居住在所罗门群岛的人群却并非来自同一地区。⁵²我们还发现，偏远波利尼西亚岛屿上的巴布亚血统与瓦努阿图的血统来源并不一致。因此，人类向太平洋的迁徙并非一次或两次，而是至少三次。第一次迁徙带来了东亚血统和拉皮塔陶器文化，而后来的迁徙则带来了至少两种不同类型的巴布亚血统。所以，人类向太平洋的扩散并非一个简单的故事，而是一个极其复杂的过程。

Ancient DNA from the Southwest Pacific has continued to produce unexpected findings. When we and Johannes Krause’s laboratory, working independently, analyzed the Papuan ancestry in Vanuatu, we found that it was more closely related to that in groups currently living in the Bismarck Islands near New Guinea than to groups currently living in the Solomon Islands—despite the fact that the Solomon Islands are directly along the ocean sailing path to Vanuatu.⁵² We also found that the Papuan ancestry present in remote Polynesian islands is not consistent with coming from the same source as that in Vanuatu. Thus there must have been not one, not two, but at least three major migrations into the open Pacific, with the first migration bringing East Asian ancestry and the Lapita pottery culture, and the later migrations bringing at least two different types of Papuan ancestry. So instead of a simple story, the spread of humans into the open Pacific was highly complex.

我们是否有可能重现这些迁徙的细节？我们完全有理由抱有希望。得益于对该地区古代DNA的获取，以及一些岛屿由于与大陆地区隔绝而人口历史相对简单，使得我们更容易还原当时的景象，我们对太平洋岛屿现代人口形成过程的了解正变得越来越清晰。通过对现代和古代人群进行全基因组研究，我们很快就能更准确地了解人类如何在这片广袤的土地上迁徙。

Can we ever hope to reconstruct the details of these migrations? There is every reason to be hopeful. Our picture of how the present-day populations of the Pacific islands formed is becoming increasingly clear thanks to access to ancient DNA from the region, and the fact that some islands have less complex population histories than mainland groups because of their isolation, permitting easier reconstruction of what occurred. Through genome-wide studies of modern and ancient populations, we will soon have a far more accurate picture of how humans moved through this vast region.

但目前我们对东亚大陆历史的了解仍然模糊不清且十分有限。汉族在过去两千年间的迅猛扩张，在原本就错综复杂的东亚人口结构上又增添了一层大规模的种族融合。而这种复杂的人口结构，必然是在该地区数千年农业发展以及石器时代、铜器时代、青铜时代和铁器时代各个族群兴衰更迭之后形成的。这意味着，任何试图基于现代人群的变异模式来重构东亚深远人口历史的尝试，都必须格外谨慎。

But right now our understanding of what happened in mainland East Asia remains murky and limited. The extraordinary expansion of the Han over the last two thousand years has added one more level of massive mixing to the already complex population structure that must have been established after thousands of years of agriculture in the region, and after the rise and fall of various Stone Age, Copper Age, Bronze Age, and Iron Age groups. This means that any attempt to reconstruct the deep population history of East Asia based on patterns of variation in present-day people must be viewed with great caution.

但当我撰写本章时，古DNA革命的浪潮正汹涌澎湃，即将席卷东亚海岸。中国已建立起最先进的古DNA实验室，正致力于研究数十年来收集的骨骼标本。对这些骨骼及其他骨骼的古DNA研究，将重构古代东亚大陆各文化群体彼此之间以及与现代人类之间的关系。我们对这种深层相互关系的理解也将因此而不断加深。东亚人祖先的船只，以及自上次冰河时代结束以来人口的迁徙，很快就会像我们对欧洲所发生事件的了解一样清晰明了。

But as I write this chapter, the tsunami of the ancient DNA revolution is cresting, and it will shortly crash on East Asian shores. State-of-the-art ancient DNA laboratories have been founded in China, and are turning their powers to investigating collections of skeletal material that have been assembled over decades. Ancient DNA studies of these and other skeletons will reconstruct how the peoples of each ancient mainland East Asian culture relate to each other and to people living today. Our understanding of the deep interrelationships of the ancestral populations of East Asians, and of movements of people since the end of the last ice age, will soon be as clear as our understanding of what happened in Europe.

但东亚古代DNA研究的结果难以预测。虽然我们对欧洲的历史已经有了较为清晰的了解，但欧洲的情况并不能为东亚的未来发展提供有效的参考，因为东亚在过去一万年的一些重大经济和技术进步中处于边缘地位，而中国则处于农业等变革的中心。这意味着，虽然我们可以肯定东亚古代DNA研究的发现将具有启发意义，但我们目前尚不清楚具体内容。我们唯一可以确定的是，古代DNA研究将改变我们对这个世界人口最稠密地区人类历史的认知。

But it is hard to predict what ancient DNA studies in East Asia will show. While we are beginning to have a relatively good idea of what happened in Europe, Europe does not provide a good road map for what to expect for East Asia because it was peripheral to some of the great economic and technological advances of the last ten thousand years, whereas China was at the center of changes like the local invention of agriculture. What this means is that while we can be sure that the findings from ancient DNA studies in East Asia will be illuminating, we do not yet know what they will be. All we can be sure of is that ancient DNA studies will change our understanding of the human past in this most populous part of the world.

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将非洲重新融入人类故事

Rejoining Africa to the Human Story

对我们非洲家园的新视角

A New Perspective on Our African Homeland

人们普遍认识到非洲在人类历史中的核心地位，但这反而分散了人们对过去五万年史前史的关注。对五万年前非洲历史的深入研究，源于人们普遍认识到非洲中石器时代向晚期石器时代过渡以及非洲近郊中旧石器时代向晚期旧石器时代过渡的重要性——这些在考古记录中得到证实的、人类行为向现代性显著飞跃的时期。然而，学者们对这一时期之后的非洲却鲜有研究。我参加讲座时，经常听到有人脱口而出“我们离开了非洲”，仿佛现代人类故事的主角必须一路追随到欧亚大陆。这种误解认为，一旦非洲孕育了非非洲人的祖先，非洲的故事就结束了，而留在非洲大陆的人们则成了静止的过去遗迹，被抛出了主线剧情，在过去的五万年里一成不变。

The recognition that Africa is central to the human story has, paradoxically, distracted attention from the last fifty thousand years of its prehistory. The intensive study of what happened in Africa before fifty thousand years ago is motivated by a universal recognition of the importance of the Middle to Later Stone Age transition in Africa and the Middle to Upper Paleolithic transition at the doorstep of Africa, those great leaps forward in recognizably modern human behavior attested to in the archaeological record. However, scholars have shown limited interest in Africa after this period. When I go to talks, a common slip of the tongue is that “we left Africa,” as if the protagonists of the modern human story must be followed to Eurasia. The mistaken impression is that once Africa gave birth to the ancestral population of non-Africans, the African story ended, and the people who remained on the continent were static relics of the past, jettisoned from the main plot, unchanging over the last fifty thousand years.

我们目前掌握的关于过去五万年欧亚大陆人类历史的丰富信息，与同期非洲信息的匮乏形成了鲜明的对比。在欧洲，大部分研究都集中于此，考古学家已经记录了一系列详细的……文化变迁：从尼安德特人到奥瑞纳文化之前的现代人类，再到奥瑞纳文化、格拉维特文化、中石器时代文化，直至石器时代的农民及其在铜器时代、青铜时代和铁器时代的后继者。古代DNA革命——其样本主要来自欧亚大陆，尤其是欧洲——进一步扩大了我们对非洲史前史的了解与对欧亚大陆史前史的了解之间的差距。

The contrast between the richness of the information we currently have about the human story in Eurasia over the last fifty thousand years and the dearth of information about Africa over the same period is extraordinary. In Europe, where most of the research has been done, archaeologists have documented a detailed series of cultural transformations: from Neanderthals to pre-Aurignacian modern humans, to Aurignacians, to Gravettians, to the people who practiced Mesolithic culture, and then to Stone Age farmers and their successors in the Copper, Bronze, and Iron ages. The ancient DNA revolution—which has disproportionately sampled bones from Eurasia and especially from Europe—has further widened the gap in our understanding of the prehistory of Africa compared to that of Eurasia.

当然，所有深入探究的研究都表明，留在非洲的人们与移居者的后代一样，都发生了巨大的变化。我们对现代非洲人类历史了解甚少的主要原因是缺乏研究。过去数万年来，非洲的人类历史是我们物种历史不可或缺的一部分。虽然将非洲视为我们物种的起源地似乎凸显了非洲的重要性，但矛盾的是，这反而会损害非洲，因为它转移了人们对留在非洲的人群如何演变成今天这种样貌的关注。借助古代和现代的DNA，我们可以弥补这一缺憾。

But of course, what all investigations that scratch below the surface show is that the people “left behind” in Africa changed just as much as the descendants of the people who emigrated. The main reason we don’t know as much about the modern human story in Africa is lack of research. Human history over the last tens of thousands of years in Africa is an integral part of the story of our species. Focusing on Africa as the place where our species originated, while it might seem to highlight the importance of Africa, paradoxically does Africa a disservice by drawing attention away from the question of how populations that remained in Africa got to be the way they are today. With ancient and modern DNA, we can rectify this.

塑造现代人类的深层混合物

The Deep Mixture That Formed Modern Humans

2012年，莎拉·蒂什科夫及其同事研究了远古人类基因混合对现代非洲人基因组的生物学影响，但他们无法获得尼安德特人和丹尼索瓦人等古代人类的基因组数据，而这些古代人类的基因组数据曾被用于记录欧亚大陆远古人类与现代人类之间的基因交流。 ¹

In 2012, Sarah Tishkoff and her colleagues studied the biological impact of archaic admixture on the genomes of present-day Africans without access to ancient genomes like those of Neanderthals and Denisovans that had been used to document interbreeding between archaic and modern humans in Eurasia.¹

蒂什科夫和她的同事对非洲一些最多样化人群的基因组进行了测序，并分析了他们的数据，以寻找一种与古人类杂交相关的模式：与绝大多数其他基因组相比，存在大量差异密度极高的DNA片段，这与起源于一个高度分化的人群相符，该人群直到最近才与现代人类融合。2^当他们将这种方法应用于当今非非洲人群时，他们提取出了这些片段。他们发现的DNA片段几乎与尼安德特人的序列完全匹配。蒂什科夫及其同事还在现代非洲人身上发现了大段与尼安德特人差异极大的序列，而这些非洲人的祖先并没有与尼安德特人混血。由于尼安德特人对非洲人的祖先贡献甚微，甚至可能没有贡献，这很可能是由于与一些神秘的非洲古人类——尚未被测序的“幽灵人群”——混血所致。

Tishkoff and her colleagues sequenced genomes from some of the most diverse populations of Africa and analyzed their data to search for a pattern that is predicted when there has been interbreeding with archaic humans: very long stretches of DNA that have a high density of differences compared to the great majority of other genomes, consistent with an origin in a highly divergent population that was isolated until recently from modern humans.² When they applied this approach to present-day non-Africans, they pulled out stretches of DNA that they found were nearly exact matches to the Neanderthal sequence. Tishkoff and her colleagues also found long stretches of deeply divergent sequences in present-day Africans whose ancestors did not mix with Neanderthals. Since Neanderthals have contributed little if any ancestry to Africans, this was likely to have been the result of mixture with mystery African archaic humans—ghost populations whose genomes have not yet been sequenced.

杰弗里·沃尔和迈克尔·哈默利用相同的基因标记，试图了解古代人群与现代非洲人之间的关系。他们估计，古代人群大约在70万年前与现代非洲人类的祖先分离，并在大约3.5万年前重新混合，贡献了现代非洲部分人群约2%的祖先成分。^然而，由于人类基因突变率的不确定性以及沃尔和哈默分析的数据量有限，我们必须谨慎看待这些时间节点和估计的混合比例。

Jeffrey Wall and Michael Hammer, using the same types of genetic signatures, attempted to learn something about the relationship of the archaic populations to present-day Africans.³ They estimated that the archaic population separated from the ancestors of present-day humans in Africa about seven hundred thousand years ago and remixed around thirty-five thousand years ago, contributing about 2 percent of the ancestry of some present-day African populations. However, it is important to view these dates and estimated proportions of mixture with caution because of uncertainties about the rate at which mutations occur in humans and because of the limited amount of data Wall and Hammer analyzed.

现代人类与古人类在撒哈拉以南非洲地区混血的可能性令人振奋，甚至在西非发现了距今11000年前的人类遗骸，这些遗骸具有古人类特征，为古人类和现代人类在非洲共存直至近代的观点提供了骨骼证据。^因此，正如在欧亚大陆一样，随着现代人类在非洲的扩张，他们与古人类杂交的机会也十分充足。

The possibility of admixture between modern and archaic humans in sub-Saharan Africa is exciting, and there are even human remains from West Africa dating to as late as eleven thousand years ago with archaic features, providing skeletal evidence in support of the idea that archaic and modern human populations coexisted in Africa until relatively recently.⁴ Thus, there were ample opportunities for interbreeding with archaic humans as modern humans expanded in Africa, just as in Eurasia.

如果如沃尔和哈默估计的那样，与古非洲人类的基因混合比例仅为2%左右，那么它可能只产生了微弱的生物学影响，类似于尼安德特人和丹尼索瓦人对非洲以外现代人群基因构成的影响。然而，这并不排除在非洲远古时期发生大规模基因混合事件的可能性。现代人类群体在撒哈拉以南非洲地区发生深度基因混合的最佳证据来自基因突变的频率。基因突变发生后的一代中，由于仅存在于一个人身上，因此极其罕见。在随后的几代中，基因突变的频率会随机地上下波动，具体取决于……它恰好遗传给了后代的数量。大多数突变永远不会达到显著的频率，因为少数携带突变的个体最终都不会将其遗传给后代，导致突变频率波动至0%并永远消失。

If the proportion of admixture with archaic African humans was only around 2 percent as Wall and Hammer estimated, it is likely to have had only a modest biological effect, similar to the effect of the contribution of Neanderthals and Denisovans to the genetic makeup of present-day people outside Africa. However, this does not rule out the possibility of major mixture events in deep African history. The best evidence for deep mixture of modern human populations in sub-Saharan Africa comes from the frequencies of mutations. One generation after a mutation occurs, it is extremely rare as it is present in only a single person. In subsequent generations, the mutation’s frequency fluctuates upward or downward at random, depending on the number of offspring to which it happens to be transmitted. Most mutations never achieve a substantial frequency, as at some point the few individuals carrying them happen not to transmit them to their children, causing them to fluctuate down to 0 percent frequency and disappear forever.

这种不断向种群注入罕见新突变的效应是，种群中常见突变的数量预计会少于罕见突变。事实上，种群中不同突变频率的变化规律预计会遵循反比定律：频率为10%的突变数量是频率为20%的突变数量的两倍，而频率为20%的突变数量又是频率为40%的突变数量的两倍。

The effect of this constant pumping into the population of rare new mutations is that there are expected to be fewer common than rare mutations in a population. The frequencies of mutations that are variable in a population are in fact expected to follow an inverse law, with twice as many mutations that occur at 10 percent frequency as those that occur at 20 percent frequency, and twice as many of these in turn as those that occur at 40 percent frequency.

我的同事尼克·帕特森检验了这一预期，他重点研究了尼日利亚约鲁巴族人群中大量个体以及尼安德特人基因组中存在的突变。帕特森将研究^重点放在尼安德特人基因组中的突变上可谓巧妙；他知道，以这种方式发现的突变几乎肯定在人类和尼安德特人的共同祖先群体中很常见，由此推断，在他们的后代中也很常见。从数学角度来看，预期此类突变会很常见的假设恰恰被其反比定律所抵消，因此，符合这些标准的突变预计会在所有频率上均匀分布。

My colleague Nick Patterson tested this expectation, focusing on mutations present in a large sample of individuals from the Yoruba group of Nigeria that were also present in the Neanderthal genome.⁵ Patterson’s focus on mutations present in Neanderthals was clever; he knew that mutations discovered in this way were almost certainly frequent in the common ancestral population of humans and Neanderthals, and by implication in their descendants too. Mathematically, the expectation that such mutations would be common is exactly counterbalanced by the inverse law, with the result that mutations meeting these criteria are expected to be equally distributed across all frequencies.

但实际数据呈现出不同的模式。当帕特森分析现代约鲁巴人的基因序列时，他发现突变率在极高和极低的频率上都显著升高，而不是像预期那样在所有频率上均匀分布。这种“U”形突变频率分布正是古代人群混合的典型特征。两个群体分离后，每个群体都会出现随机的频率波动，因此在一个群体中频率偶然波动到0%或100%的突变，通常与在另一个群体中出现相同频率的突变并不相同。当这两个群体再次混合时，在一个群体中频率达到极端值而在另一个群体中频率未达到极端值的突变，会以可变基因型的形式重新引入。这会在混合群体中产生额外的突变密度峰值。第一个峰值对应于……预计在第一个人群中频率达到极高的突变，其起始频率将等于混合比例；而第二个高峰对应于在第二个人群中频率达到极高的突变，其起始频率将等于100%减去混合比例。这正是帕特森发现的模式，他证明，如果约鲁巴人是由两个高度分化的人群以接近相等的比例混合而成，那么这种模式就可以得到解释。

But the real data showed a different pattern. When Patterson examined sequences from present-day Yoruba, he observed a greatly elevated rate of mutations both at very high and low frequencies, instead of an equal distribution across all frequencies. This “U-shaped” distribution of mutation frequencies is what would be expected in the case of ancient mixture. After two populations separate, random frequency fluctuation occurs in each population, so that the mutations that fluctuate by chance to 0 percent or 100 percent frequency in one population are by and large not expected to be the same as those that do so in the other population. When the populations then remix, the mutations that rose to extreme frequencies in one population but not in the other would be reintroduced as variable genetic types. This would produce peaks of extra mutation density in the mixed population. The first peak corresponding to mutations that rose to extreme frequencies in the first population is expected to start at the proportion of mixture, while the second peak corresponding to mutations that rose to extreme frequencies in the second population is expected to start at 100 percent minus the proportion of mixture. This is exactly the pattern that Patterson found, and he showed that it could be explained if Yoruba descended from a mixture of two highly differentiated human populations in close to equal proportions.

帕特森检验了他观察到的模式是否与这样一种模型相符：只有约鲁巴人是这种混合血统的后裔，而非非洲人则不是。但数据与此相悖。相反，所有非非洲人——甚至包括像桑人狩猎采集者这样不同的非洲血统——似乎也都源自类似的混合血统。因此，尽管帕特森最初研究的是西非人，但他发现的混合事件并非该人群所特有。相反，这似乎是现代人类祖先共同经历的事件，表明这种混合可能发生在大约30万年前，也就是解剖学意义上的现代人类特征首次出现在骨骼记录中前后。 ⁶

Patterson tested whether the patterns he observed were consistent with a model in which only Yoruba descend from this mixture but non-Africans do not. But this was contradicted by the data. Instead, all non-Africans—and even divergent African lineages such as San hunter-gatherers—also seem to be descended from a similar mixture. Thus, although Patterson had begun by looking at West Africans, the mixture event he detected was not specific to that population. Rather, it seemed to be a shared event in the ancestry of present-day humans, suggesting that the mixture may have occurred close to the time when anatomically modern human features first appear in the skeletal record after around three hundred thousand years ago.⁶

帕特森的研究结果与李恒和理查德·德宾（在第一部分中讨论过）2011年的一项研究发现相呼应，该研究利用单个个体的基因组重建了人类种群规模的历史。 ⁷该研究比较了一个人从母亲那里遗传的基因组序列和从父亲那里遗传的基因组序列。研究发现，在基因组中，共同祖先的重建年龄落在40万年前到15万年前之间的位置比假设人口规模恒定时预期的数量要少。 ⁸对此结果的一种可能解释是，所有现代人类的祖先在这一时期的人口规模非常庞大，这意味着今天任意两个基因组在那个时期拥有共同祖先的概率很小（因为每一代都有许多可能的祖先）。但另一种可能性是，人类祖先并非由单一的、自由混合的群体组成，而是由多个高度分化的群体构成，因此，现代人类的祖先谱系在当时被隔离在不同的群体中。这种模式可能反映了帕特森在其著作中强调的同一混合事件。对突变频率的研究。重建的时间与非洲古代人类骨骼形态与现代人类骨骼形态重叠的时期相对应。例如，最近在南非一个洞穴中发现的纳莱迪人骨骼，其身体结构相对现代，但大脑比现代人类小得多，其年代可追溯到34万至23万年前^。9

Patterson’s findings resonated with a discovery from the 2011 study by Heng Li and Richard Durbin (discussed in part I) that reconstructed human population size history from a single person’s genome.⁷ That study compared the genome sequence a person gets from his or her mother to the sequence he or she gets from his or her father. It found fewer locations in the genome where the reconstructed age of the shared ancestor falls between 400,000 and 150,000 years ago than would be expected if the population had been constant in size.⁸ One possible explanation for this result is that the ancestral population of all modern humans was very large over this period, which would mean that the probability that any two genomes today share a particular ancestor at this time is small (there being many possible ancestors in each generation). But the other possibility was that the ancestral human population consisted of multiple highly divergent groups instead of a single, freely mixing group, and hence the lineages ancestral to present-day people were isolated in separate populations at this time. This pattern could be reflecting the same mixture event that Patterson had highlighted through his study of mutation frequencies. The reconstructed time corresponds to a period when there is skeletal evidence of archaic human forms overlapping with modern human forms in Africa. For example, the Homo naledi skeletons recently discovered in a cave in South Africa had relatively modern human bodies but brains much smaller than those of modern humans, and date to between 340,000 and 230,000 years ago.⁹

还有第三条证据支持远古混血的观点。一种普遍的观点认为，南部非洲的桑人狩猎采集者主要源自一个谱系，该谱系在与其他现代人类谱系分化之前，从该谱系中分叉而出。 ¹⁰ 如果真是如此，桑人与所有非南部非洲人共享突变的频率应该完全相同。但我实验室的庞图斯·斯科格伦德（Pontus Skoglund）的研究表明，桑人与东非和中非狩猎采集者共享的突变比与西非人群（例如尼日利亚的约鲁巴人）共享的突变更多。 ¹¹如果西非人群比非非洲人群拥有更多来自早期分化人群的祖先成分，则可以解释这一现象。或许所有现代人类都是两个高度分化的祖先群体的混合体，其中西非人群所占比例最大，但所有人群都继承了来自这两个群体的DNA。

There was also a third line of evidence for archaic mixture. A commonly held view is that the San hunter-gatherers of southern Africa largely derive from a lineage that branched off the one leading to all other present-day modern human lineages before they separated from one another.¹⁰ If so, the San would be expected to share mutations at exactly the same rate with all non–southern Africans. But Pontus Skoglund in my laboratory showed that the San share more mutations with eastern and central African hunter-gatherers than they do with West African populations like the Yoruba of Nigeria.¹¹ This could be explained if the West African populations harbor more ancestry from one of the early-splitting populations than is the case for non-African populations. Perhaps all present-day humans are a mixture of two highly divergent ancestral groups, with the largest proportion in West Africans, but all populations inheriting DNA from both.

这些结果表明，非洲大规模的种族融合可能发生在大约五万年前，也就是现代人类行为在考古记录中全面爆发之前很久。这种融合并非微不足道，不像非非洲人中约2%的尼安德特人血统，或者沃尔和哈默在非洲人身上发现的“幽灵般的古老祖先”。由于这种融合接近50/50，甚至难以确定哪个来源人群应该被视为古老人群，哪个应该被视为现代人群。或许两者都不是现代人群，或者两者都不是古老人群。或许这种融合本身对于塑造现代人类至关重要，它将两个混合人群的生物特征融合在一起，并以有利于新形成人群的方式结合起来。

These results suggest the possibility that major mixture in Africa occurred in the time well before around fifty thousand years ago when modern human behavior burst into full flower in the archaeological record. This mixture wasn’t a minor event, such as the approximately 2 percent Neanderthal admixture in non-Africans or the ghost archaic ancestry in Africans found by Wall and Hammer. Because this mixture was closer to 50/50, it is not even clear which one of the source populations should properly be considered archaic and which modern. Perhaps neither was modern, or neither was archaic. Perhaps the mixture itself was essential to forging modern humans, bringing together biological traits from the two mixing populations and combining them in new ways that were advantageous to the newly formed populations.

农业如何掩盖了非洲的过去

How Agriculture Threw a Veil over Africa’s Past

我们如何才能了解现代人类祖先群体形成之后，以及大约五万年前现代非非洲人的祖先从非洲和近东地区扩散之后，非洲发生了什么？我们有很多信息可以利用，因为非洲人的基因组序列通常比非非洲人的基因组序列多样性高出约三分之一。非洲的人类多样性不仅体现在群体内部，也体现在群体之间。一些非洲人群的隔离时间比非洲大陆以外的任何人群隔离时间长达四倍之久。这体现在某些人群——例如来自南部非洲的桑人狩猎采集者和来自西非的约鲁巴人——的基因组突变最小密度远高于非洲以外任何人群基因组的突变最小密度。 ¹²

How can we begin to learn what happened in Africa after the ancestral population of modern humans was forged, and also after the ancestors of present-day non-Africans spread out of Africa and the Near East beginning around fifty thousand years ago? There is a lot of information to work with, as African genome sequences are typically about a third more diverse than non-African ones. Human diversity in Africa is extraordinary not only within but also across populations, as some pairs of African populations have been isolated for up to four times longer than any pairs of populations outside the continent, as reflected by the fact that for some pairs of populations—like San hunter-gatherers from southern Africa and Yoruba from West Africa—the minimum density of mutations separating their genomes is that much greater than that for any pair of genomes outside Africa.¹²

但从当今人群中了解非洲人的远古历史极其困难，因为尽管古代的各种物种大多……种族融合仍然存在于当今的人群中，只是形式多种多样，混杂在一起。最近一次人口融合发生在过去几千年，至少经历了四次大规模扩张，每次扩张都与语言群体的传播有关，其中大部分是由农业人口的扩散推动的。 ¹³这些扩张掩盖了非洲的过去，将人口从其起源地迁徙了数千公里，在那里，他们与先前广泛分布的人口发生了冲突或融合。从这个角度来看，对非洲人口的研究与对欧亚大陆人口的研究并无二致，后者在过去几千年中也经历了人口更迭。

But learning about Africans’ deep past from today’s populations is extremely challenging because while much of the ancient variation still exists in people living today, it is all mixed up. The most recent mixing of populations occurred in the last few thousand years due to at least four great expansions, all of which are associated with the spread of language groups, and most of which have been driven by the spread of agriculturalists.¹³ These expansions have thrown a veil over the African past, moving populations thousands of kilometers from their places of origin, where they displaced or mixed with populations that were widespread before. In this respect, the study of African populations is no different from the study of Eurasian ones, which have also turned over in the last several thousand years.

对非洲影响最大的农业扩张与班图语系人群密切相关。^考古研究表明，大约四千年前，一种新的文化从尼日利亚和喀麦隆交界的西非中部地区传播开来。这种文化的人们生活在森林与不断扩张的稀树草原的交界处，发展出一套高产的作物，足以养活大量的人口。大约两千五百年前，他们的足迹已远至东非的维多利亚湖，并掌握了铁器制造技术；大约一千七百年前，他们到达了南部非洲。这种扩张的结果是，^{东非、中非和南部非洲的绝大多数人都讲班图语，而如今}班图语在喀麦隆最为多样化。这与原始班图语起源于喀麦隆，并由大约四千年前从那里扩张的文化传播开来的理论相符。¹⁸班图语是尼日尔-科尔多凡语系的一个子集，该语系涵盖了西非的大部分语言，¹⁹这可能解释了为什么尽管尼日利亚和赞比亚这两个国家之间的地理距离要大得多，但如今这两个国家语言群体的突变频率却比德国和意大利的语言群体的突变频率更为相似。

The agriculturalist expansion that had the greatest impact on Africa is the one associated with people who speak languages of the Bantu family.¹⁴ Archaeological studies have documented how beginning around four thousand years ago, a new culture spread out of the region at the border of Nigeria and Cameroon in west-central Africa. People from this culture lived at the boundary of the forest and expanding savanna and developed a highly productive set of crops that was capable of supporting dense populations.¹⁵ By about twenty-five hundred years ago they had spread as far as Lake Victoria in eastern Africa and mastered iron toolmaking technology,¹⁶ and by around seventeen hundred years ago they had reached southern Africa.¹⁷ The consequence of this expansion is that the great majority of people in eastern, central, and southern Africa speak Bantu languages, which are most diverse today in present-day Cameroon, consistent with the theory that proto-Bantu languages originated there and were spread by the culture that also expanded from there around four thousand years ago.¹⁸ Bantu languages are a subset of the larger Niger-Kordofanian family spanning most of the languages of West Africa,¹⁹ which likely explains why today the frequencies of mutations in groups in Nigeria and in Zambia are more similar than the frequencies of mutations in Germany and Italy despite the former two countries being separated by a far greater geographic distance.

超灵敏的基因检测方法能够检测出过去几千年内个体间的共同亲缘关系，这使得了解人类的地理迁徙路径成为可能。班图人的扩张。东非班图语人群的遗传变异与中非雨林以南马拉维的遗传变异关系更为密切，而非与喀麦隆的遗传变异关系密切。 ²⁰这表明，班图人的最初扩张主要向南进行，而向东非的迁徙则是从南部的一个中转站后来发生的扩张。这与从喀麦隆直接向东迁徙的理论相悖，而该理论在遗传数据出现之前曾被认为是合理的。

Ultra-sensitive genetic methods, which can detect shared relatives of pairs of individuals in the past few thousand years, have now made it possible to learn something about the geographic path of the Bantu expansion. The genetic variation in Bantu speakers in East Africa is more closely related to the genetic variation in Malawi to the south of the Central African rainforests than it is to genetic variation in Cameroon.²⁰ This suggests that the initial Bantu expansion was largely to the south and that the movement to East Africa was a later expansion from a southern staging ground. This contrasts with the theory of a direct eastward movement from Cameroon, a theory that had been plausible prior to the genetic data.

另一项影响深远的农业扩张是尼罗-撒哈拉语系的传播，该语系的使用者遍布从马里到坦桑尼亚的广大地区。许多尼罗-撒哈拉语系的使用者是牧民，一种普遍的观点认为，尼罗-撒哈拉语系的扩张是由过去五千年来撒哈拉沙漠扩张过程中，非洲干旱的萨赫勒地区农业和畜牧业的传播所驱动的。尼罗语系的一个重要分支是尼罗语族，主要由尼罗河沿岸和东非的牧民使用，包括马赛人和丁卡人。基因数据表明，在他们所处的边远地区，尼罗语族牧民的社会地位并非总是低于农民。彼此之间相互影响。例如，肯尼亚西部的卢奥族（美国前总统奥巴马的父亲就属于这个族群）主要以务农为生，讲尼罗语系语言。但曾在我实验室工作过的肯尼亚卢奥族科学家乔治·阿约多发现，卢奥族的基因突变频率与大多数班图语使用者更为相似，这可能反映了东非一个班图语族群从其地位较高的邻国那里吸收了一种尼罗-撒哈拉语系语言的历史^。21

Another agricultural expansion that had a profound impact is the one that spread Nilo-Saharan languages, spoken by groups from Mali to Tanzania. Many Nilo-Saharan speakers are cattle herders, and a common view is that the Nilo-Saharan expansion was driven by the spread of farming and herding in Africa’s dry Sahel region during the expansion of the Sahara Desert over the last five thousand years. One important branch of Nilo-Saharan is the Nilotic languages, which are mostly spoken by cattle herders along the Nile River and in East Africa, including the Maasai and Dinka. The genetic data make it clear that Nilotic-speaking herders were not always socially disadvantaged relative to farmers in the frontier regions where they encountered each other. For example, the Luo group of western Kenya (to which former U.S. president Barack Obama’s father belonged) are a primarily farming people who speak a Nilotic language. But George Ayodo, a Luo scientist from Kenya who spent time in my laboratory, found that the mutation frequencies in the Luo are much more similar to those of the majority of Bantu speakers, likely reflecting a history in which a Bantu-speaking group in East Africa adopted a Nilo-Saharan language from its high status neighbors.²¹

非洲语言扩张中，起源最不明朗的是与亚非语系相关的语言扩张。这些语言在今天的埃塞俄比亚最为多样化，这有力地支持了东北非是这些语言最初使用者故乡的理论。 ²²但亚非语系也包含一个分布于近东的语支，其中包括阿拉伯语、希伯来语和古阿卡德语。基于此，有人假设亚非语系语言的传播，或者至少是其中某些语支的传播，可能与近东农业的传播有关。 ²³近东农业在七千年前将大麦、小麦和其他作物引入了东北非。 ²⁴古DNA研究已经带来了新的发现，它使得记录近东和北非之间可能传播语言、文化和作物的古代迁徙成为可能。 2016年和2017年，我的实验室发表了两篇论文，指出许多东非人群（包括一些不讲亚非语系语言的人群）的一个共同特征是，他们拥有大量来自约一万年前生活在近东的农民的祖先血统。 ²⁵我们的研究还发现了强有力的证据，表明存在第二波与西欧亚相关的基因混合——这次的混合来自伊朗裔农民，这与青铜时代近东人口的扩散预期相符——并且表明，这种祖先血统广泛存在于当今索马里和埃塞俄比亚讲库希特语族亚非语系语言的人群中。因此，遗传数据提供了证据，表明在亚非语系语言传播和多样化的时期，至少发生了两次主要的由北向南的人口迁徙，而没有证据表明存在由南向北的迁徙（古代近东人或埃及人几乎没有撒哈拉以南非洲相关的祖先血统）。（中世纪之前）。26^基因并不能决定一个人说什么语言，因此基因数据本身无法确定语言是如何传播的，也无法为亚非语系语言的最终起源地是撒哈拉以南非洲、北非、阿拉伯半岛还是近东这一理论提供确凿的证据。但毫无疑问，基因数据增加了近东农业文明至少是部分亚非语系语言起源的可能性，并且这些基因发现也引发了人们对这些由北向南迁徙的人们究竟说了什么语言的思考。

The African language expansion whose origin is most unclear is the one associated with Afroasiatic languages. They are most diverse in present-day Ethiopia, which throws weight behind the theory that northeastern Africa was the homeland of the original speakers of these languages.²² But the Afroasiatic language family also contains a branch localized to the Near East that includes Arabic, Hebrew, and ancient Akkadian. It has been hypothesized on this basis that the spread of Afroasiatic languages, or at least some branches of them, could have been related to the spread of Near Eastern agriculture,²³ which introduced barley and wheat and other Near Eastern crops into northeast Africa up to seven thousand years ago.²⁴ New insights are already emerging from ancient DNA, which makes it possible to document ancient migrations between the Near East and North Africa that could have spread languages, culture, and crops. In 2016 and 2017, my laboratory published two papers showing that a shared feature of many East African groups, including ones that do not speak Afroasiatic languages, is that they harbor substantial ancestry from people related to farmers who lived in the Near East around ten thousand years ago.²⁵ Our work also found strong evidence for a second wave of West Eurasian–related admixture—this time with a contribution from Iranian-related farmers as might be expected from a spread from the Near East in the Bronze Age—and showed that this ancestry is widespread in present-day people from Somalia and Ethiopia who speak Afroasiatic languages in the Cushitic sub-family. So the genetic data provide evidence for at least two major waves of north-to-south population movement in the period when Afroasiatic languages were spreading and diversifying, and no evidence of south-to-north migration (there is little if any sub-Saharan African related ancestry in ancient Near Easterners or Egyptians prior to medieval times).²⁶ Genes do not determine what language a person speaks and so genetic data cannot by themselves determine how languages spread, and thus cannot provide definitive evidence in favor of one theory or another about whether the ultimate homeland of Afroasiatic languages was sub-Saharan Africa, North Africa, Arabia, or the Near East. But there is no question that the genetic data increase the plausibility of a Near Eastern agriculturalist source for at least some Afroasiatic languages, and the genetic findings raise the question of what languages were spoken by these north-to-south migrants.

非洲第四次农业扩张与南部非洲的科伊-夸迪语系密切相关。与南部非洲狩猎采集群体所使用的两个语系——克萨语和图语——一样，科伊-夸迪语也以吸气音为特征。基于与放牧相关的词汇，有人假设科伊-夸迪语是由1800年后从东非来到南部非洲的牧牛人带入的，他们可能也从当地居民那里习得了吸气音。 ²⁷遗传数据支持东非人对当今科伊-夸迪语人群的基因构成做出重大贡献的假设。2012年，我实验室的约瑟夫·皮克雷尔（Joseph Pickrell）的研究表明，与克萨语和图语相比，科伊-夸迪语使用者与埃塞俄比亚人的祖先共享比例过高，这与来自北方的迁徙预期相符。²⁸在一些科伊夸迪语系人群中，源自东非的DNA片段的大小与18至900年前与一个“幽灵牧民”群体混合的预期大小相符，这与牧民大约在这一时期抵达以及与当地人群混合完成前的延迟相一致。在与东非人匹配的片段中，皮克雷尔发现了更小的片段，这些片段与近东人的匹配度高于与其他任何人群的匹配度，其长度符合大约3000年前的平均混合时间预期。这与埃塞俄比亚许多人群中西欧亚相关祖先和撒哈拉以南祖先的平均混合时间相符，²⁹因此，这一发现进一步支持了东非起源的假设。

The fourth great agriculturalist expansion in Africa is the one associated with the Khoe-Kwadi languages of southern Africa. Like the two language groups spoken by hunter-gatherer groups in the south of Africa—Kx’a and Tuu—Khoe-Kwadi languages are characterized by click sounds. Based on shared words for herding, it has been hypothesized that Khoe-Kwadi languages were brought from East Africa by cattle herders who came to southern Africa after eighteen hundred years ago and who may also have picked up click sounds from local populations.²⁷ The genetic data support the hypothesis of a major genetic contribution by East Africans to Khoe-Kwadi-speaking populations today. In 2012, Joseph Pickrell in my laboratory showed that Khoe-Kwadi speakers share a disproportionate amount of their ancestry with Ethiopians compared to the Kx’a and the Tuu, as might be expected from a migration from the north.²⁸ The size of East African–derived DNA segments in some of the Khoe-Kwadi–speaking populations is what would be expected from mixture eighteen to nine hundred years ago with a ghost herder population, consistent with the arrival of herders around this time and a delay before the mixture with local populations was complete. Within the segments matching East Africans, Pickrell found even smaller segments that matched Near Easterners more than they did any other populations, and that had lengths expected for an average mixture date of around three thousand years ago. That is the average date of mixture between people of West Eurasian–related ancestry and sub-Saharan ancestry in many groups in Ethiopia,²⁹ so this finding provides further support for the hypothesis of an East African source.

古代DNA如今证实了这一假设。2017年，庞图斯·斯科格伦德（Pontus Skoglund）分析了来自赤道东非坦桑尼亚的一具约3100年前女婴遗骸的古代DNA，以及来自南非西开普省的一具约1200年前的样本。这两具遗骸均埋葬于文物和动物骨骼之中，这些文物和骨骼表明它们来自牧民群体。 ³⁰这名坦桑尼亚女婴属于皮克雷尔和我预测的“幽灵牧民”群体：该群体的大部分祖先来自古代东非狩猎采集者，其余部分来自与古代西欧亚大陆相关的群体。几乎可以肯定的是，该群体在将畜牧业从近东和北非传播到撒哈拉以南非洲的过程中发挥了重要作用。我们从这位南部非洲牧民身上获得的古代DNA证据也强有力地支持了这一观点。该证据表明，这位牧民约三分之一的祖先来自与坦桑尼亚女孩同属一个畜牧群体的人群，其余祖先则来自与现代桑人狩猎采集者相关的当地族群。这位生活在1200年前的南部非洲牧民的祖先构成与现代科伊-夸迪语使用者（其中许多人也是牧民）的祖先构成非常相似，这支持了这样一种理论：早期科伊-夸迪语、畜牧业以及这种东非祖先构成都是通过人口迁徙传播到南部非洲的。

Ancient DNA has now verified this hypothesis. In 2017, Pontus Skoglund analyzed ancient DNA from the approximately thirty-one-hundred-year-old remains of an infant girl from Tanzania in equatorial East Africa, and an approximately twelve-hundred-year-old sample from the western Cape region of South Africa, both buried among artifacts and animal bones that identified them as being from herder populations.³⁰ The Tanzanian girl was a member of the ghost herding population that Pickrell and I had predicted: a group that derived most of its ancestry from ancient East African hunter-gatherers, and the remaining part from an ancient West Eurasian–related population. This population almost certainly played a major role in spreading cattle herding from the Near East and North Africa across sub-Saharan Africa. Our ancient DNA evidence from the southern African herder also strongly supported this idea, showing that this individual derived about one-third of her ancestry from the pastoralist population of which the Tanzanian girl was a part, and her remaining ancestry from local groups related to present-day San hunter-gatherers. The mixture of ancestries in the twelve-hundred-year-old southern African herder was very similar to that in present-day Khoe-Kwadi speakers, many of whom are herders, supporting the theory that early Khoe-Kwadi languages, herding, and this type of East African ancestry all spread to southern Africa through a movement of people.

如今非洲人类生物和文化的多样性令人叹为观止，这主要得益于过去几千年来农业扩张的影响。然而，如果想要了解非洲历史的全貌，这种多样性反而会分散注意力。非洲遗传学、考古学和语言学研究人员常常陷入一个误区：过分强调非洲当下的多样性。例如，在介绍非洲时，我们经常会使用一张幻灯片，上面展示了来自非洲各地的人们，他们的外貌千差万别。人们很容易认为，要理解非洲的深远历史，就必须能够将所有这些多样性都囊括其中，并一一解释清楚。但事实上，非洲当今的人口结构很大程度上是由过去几千年的农业扩张塑造的。因此，仅仅关注描述非洲令人着迷的多样性，反而会阻碍我们对非洲历史的理解。仅仅关注非洲人类的整体图景是有害的，正如仅仅关注所有现代人类在非洲的共同起源也是对非洲的损害一样。我们需要停止描述那层遮蔽人类历史的面纱，而是应该揭开它，而要做到这一点，我们需要古代DNA。

The landscape of human biological and cultural diversity in Africa today, dominated as it is by the effects of the agricultural expansions of the last few thousand years, is extraordinary, but it is also distracting if one’s interest is in understanding the big picture of what happened. A trap that researchers of African genetics, archaeology, and linguistics repeatedly fall into is celebrating Africa’s present-day diversity, epitomized by a slide showing the faces of people from across the continent who look very different from each other that many of us use when presenting on Africa. It is tempting to think that in order to comprehend deep time in Africa we need to be able to hold all of that diversity in our heads and explain all of it at once. But most of the present-day population structure of Africa is shaped by the agricultural expansions of the past few thousand years, and so focusing on describing Africa’s mesmerizing diversity paradoxically does the project of understanding the big picture of humans in Africa a disservice just as much as focusing on the common origins of all modern humans in Africa does Africa a disservice. We need to stop focusing on describing the veil and instead rip it away, and for this we need ancient DNA.

重构非洲的狩猎采集时代

Reconstructing Africa’s Forager Past

在粮食生产者扩张之前，非洲居住着哪些人？是他们深刻地改变了这片大陆的人类面貌吗？仅凭当今人群的基因变异模式来回答这个问题极其困难。本书引言中，我曾描述过卢卡·卡瓦利-斯福尔扎 (Luca Cavalli-Sforza) 在 1960 年所做的一个假设：完全基于当今人群的基因变异模式，就能重建人类的远古历史。^然而，他最终失败了。古代 DNA 研究表明，人类经历了如此频繁的迁徙和灭绝，以至于在大多数情况下，即使运用复杂的统计方法，也很难从现代人 DNA 中留下的痕迹还原古代人口事件的细节。

Who lived in Africa before the expansion of food producers, the people who so profoundly transformed the human landscape of the continent? Answering this question is extraordinarily difficult based on patterns of present-day variation. In the introduction to this book, I described how Luca Cavalli-Sforza made a bet in 1960 that it would be possible to reconstruct the deep history of human populations based entirely on patterns of genetic variation in present-day groups.³¹ However, he lost his bet, as ancient DNA has revealed that there has been so much migration and population extinction that in most instances it is very difficult even with sophisticated statistical methods to recover the details of ancient demographic events from the traces left behind in the DNA of present-day people.

突破这一僵局的突破性进展对读者来说并不意外。它就是全基因组古代DNA，可以与来自那些在基因和文化上与邻近人群隔绝的群体的数据进行联合分析，例如中非的俾格米人、非洲南端的桑人狩猎采集者，以及坦桑尼亚的哈扎人。哈扎人的语言带有吸气音，与周围班图人的语言截然不同，他们的遗传祖先也极具特色。其中一些人群的遗传谱系与邻近人群的差异非常大。我们可以将这些古代样本的数据进行比较，从而探究比仅通过分析现代人群DNA所能触及的更久远的事件。

The breakthrough that is making it possible to get beyond this impasse will not be surprising to the reader. It is genome-wide ancient DNA, which can be coanalyzed with data from groups that have been genetically and culturally isolated compared to their neighbors, among them the Pygmies of Central Africa, the San hunter-gatherers of the southern tip of Africa, and the Hadza of Tanzania, whose languages with clicks are very different from the languages of the Bantu who surround them and whose genetic ancestry is highly distinctive as well. Some of these populations harbor genetic lineages that are highly divergent from their neighbors. We can compare data from these ancient samples to probe events that occurred deeper in time than those that can be accessed only by analyzing the DNA of present-day populations.

由于气候炎热，加速了导致DNA降解的化学反应，因此在非洲大部分地区，保存完好的古代DNA直到最近都很难找到。但在2015年，古代DNA的发现取得了突破性进展。由于 DNA 提取技术的效率提高以及对哪些骨骼能提取最多 DNA 的更深入了解，DNA 革命终于来到了非洲。

Well-preserved ancient DNA has until recently been hard to find in most parts of Africa because of the hot climate, which accelerates chemical reactions that degrade DNA. But in 2015, the ancient DNA revolution finally arrived in Africa because of improvements in the efficiency of DNA extraction techniques and a better understanding of which bones yielded the most DNA.

非洲首个全基因组古代DNA数据来自埃塞俄比亚高原洞穴中发现的一具距今4500年的骨骼。 ³²这位古代个体与如今生活在埃塞俄比亚的阿里人（Ari）族群的亲缘关系，远比与其他许多族群更为密切。如今，埃塞俄比亚存在着一套复杂的种姓制度，它塑造着许多人的生活，繁复的规章制度禁止不同传统角色群体之间的通婚。 ³³阿里人分为三个亚群体——耕种者、铁匠和陶工——他们在社会和基因上彼此不同，也与其他非阿里族群存在差异。 ³⁴由于阿里人与这位距今4500年的古代高原个体相比，与其他埃塞俄比亚族群相比具有显著的基因亲缘性，这表明在当今埃塞俄比亚的这一区域内，存在着强大的基因交流和同质化障碍，并且这种障碍至少持续了4500年之久。这是我所知的最典型的强内婚制案例——甚至比印度已知的内婚制证据还要古老，后者目前仅有几千年的记录^。35

The first genome-wide ancient DNA data from Africa came from a forty-five-hundred-year-old skeleton found in a highland cave in Ethiopia.³² This ancient individual was much more closely related to one group living in Ethiopia today, the Ari, than to many others. Today there is an intricate caste system that shapes the lives of many people within Ethiopia, with elaborate rules preventing marriage between groups with different traditional roles.³³ The Ari include three subgroups—the Cultivators, Blacksmiths, and Potters—who are socially and genetically differentiated from one another and from non-Ari groups.³⁴ Since the Ari have a distinctive genetic affinity to the forty-five-hundred-year-old ancient highland individual compared to other Ethiopian groups, it is clear that there were strong local barriers to gene exchange and homogenization within the region of present-day Ethiopia that persisted for at least forty-five hundred years. This is the best example of strong endogamy that I know of—even more ancient than the evidence of endogamy in India that so far is only documented as going back a couple of thousand years.³⁵

古代DNA不断给我们带来惊喜。2017年，我实验室的庞图斯·斯科格伦德（Pontus Skoglund）分析了来自非洲的16个个体：生活在约2100至1200年前的南非狩猎采集者和牧民，生活在约8100至2500年前的南部非洲马拉维的狩猎采集者，以及生活在约3100至400年前的坦桑尼亚和肯尼亚的狩猎采集者、农民和牧民。 ³⁶虽然与一些最古老的欧亚大陆古代DNA相比，这些个体的年代非常近，但它们仍然为我们了解粮食生产者到来之前非洲的人口结构提供了重要线索，而这些粮食生产者极大地改变了非洲的人类地理格局。

Ancient DNA keeps surprising us. In 2017, Pontus Skoglund in my laboratory analyzed sixteen individuals from Africa: foragers and herders from South Africa who lived between about twenty-one hundred and twelve hundred years ago, foragers from Malawi in southern Africa who lived between about eighty-one hundred and twenty-five hundred years ago, and foragers, farmers, and herders from Tanzania and Kenya who lived between about thirty-one hundred and four hundred years ago.³⁶ While these individuals are very recent compared to some of the oldest Eurasian ancient DNA, they nevertheless provide insights into African population structure before the arrival of the food producers who transformed much of Africa’s human geography.

我们从古代DNA分析中得出的一个重大发现是，有证据表明，撒哈拉以南非洲东海岸曾经存在一个庞大的“幽灵人口”，但随着农业人口的扩张，这个人口似乎已被大量取代。37^这个人口我们称之为“东非狩猎采集者”的人群，贡献了我们数据集中来自埃塞俄比亚和肯尼亚的两个古代狩猎采集者基因组的全部祖先，以及如今坦桑尼亚哈扎人（人口不足一千）的几乎所有祖先。我们还发现，东非狩猎采集者与当今非非洲人群的亲缘关系比与撒哈拉以南非洲任何其他人群的亲缘关系都更近。与非非洲人群的密切关系表明，东非狩猎采集者的祖先可能是中石器时代向晚期石器时代过渡的人群，大约五万年前，他们推动了向非洲以外地区乃至非洲内部的扩张。因此，东非狩猎采集者这一人群在我们的历史中扮演了至关重要的角色。

A great surprise that emerged from our ancient DNA analysis was that there was evidence of a ghost population dominating the eastern seaboard of sub-Saharan Africa that appears to have been largely displaced by the expansion of agriculturalists.³⁷ This population, which we called the “East African Foragers,” contributed all of the ancestry of two ancient hunter-gatherer genomes in our dataset from Ethiopia and Kenya, as well as essentially all of the ancestry of the present-day Hadza of Tanzania, who today number fewer than one thousand. We also found that the East African Foragers were more closely related to non-Africans today than they were to any other groups in sub-Saharan Africa. The close relationship to non-Africans suggests that the ancestors of the East African Foragers may have been the population in which the Middle to Later Stone Age transition occurred, propelling expansions outside of Africa and possibly within Africa too after around fifty thousand years ago. So the population that became the East African Foragers had a pivotal role in our history.

东非狩猎采集者并非同质群体。这一点从我们的数据中可以明显看出：在非洲境内至少存在三个不同的东非狩猎采集者群体——一个横跨古代埃塞俄比亚和古代肯尼亚，第二个群体构成了桑给巴尔群岛和马拉维古代狩猎采集者祖先的重要组成部分，第三个群体则体现在当今的哈扎人之中。 ³⁸由于我们掌握的数据有限，无法确定这些群体彼此分离的具体时间。但考虑到其广阔的地理跨度以及人类在该地区居住的悠久历史，这些群体之间的某些差异可以追溯到数万年前也并不令人惊讶。非洲狩猎采集群体内部出现此类分离的先例并非没有。 2012年，我所在的实验室和另一个实验室的研究表明，我称之为“南非觅食者”的群体——其与东非觅食者的分化程度与当今任何人类群体都一样显著——内部包含两个高度分化的谱系，这两个谱系至少在两万年前就已分离。^东非的人类栖息地至少与南部非洲一样丰富，因此，如果东非觅食者之间的分化至少与南部非洲一样古老，也并不令人惊讶。

The East African Foragers were not a homogeneous population. This is evident from the fact that our data include at least three distinct East African Forager groups within Africa—one spanning the ancient Ethiopian and ancient Kenyan, a second contributing large fractions of the ancestry of the ancient foragers from the Zanzibar Archipelago and Malawi, and a third represented in the present-day Hadza.³⁸ Based on the sparse data we had, we were not able to determine the date when these groups separated from one another. But given the extended geographic span and the antiquity of human occupation in this region, it would not be surprising if some of the differences among these groups dated back tens of thousands of years. There is precedent for such separations within forager populations in Africa. In 2012, my laboratory and another showed that a group that I think of as the “South African Foragers”—a lineage that is as divergent from the East African Foragers as any present-day human population—contained within it two highly divergent lineages that separated from each other at least twenty thousand years ago.³⁹ East Africa is at least as rich a human habitat as southern Africa, and it would not be surprising if separations among foragers in East Africa were at least as old.

第二个意外发现是，我们的一些古代非洲狩猎采集者人群样本同时拥有南非狩猎采集者谱系和东非狩猎采集者谱系的共同祖先。如今，南非狩猎采集者谱系基本上已经完全消失。他们分布到非洲最南端，在那里，他们构成了几乎所有使用含吸气音语言的人群祖先的重要组成部分，并且几乎贡献了当今桑人狩猎采集者的所有祖先，以及我们从南部非洲获得的古代狩猎采集者基因组。但我们的古代样本表明，“南非狩猎采集者”这个术语可能误导了人们对该群体祖先起源地的认知。来自坦桑尼亚海岸附近的桑给巴尔岛和奔巴岛的两名约1400年前的个体——该岛链大约在1万年前随着海平面上升与大陆分离，因此很可能栖息着当时生活在东非的狩猎采集者群体的孤立后裔 ⁴⁰ ——他们的祖先大约有三分之一与南非狩猎采集者有关。其余部分则来自东非狩猎采集者的祖先。41^我们在非洲中南部马拉维的三个不同考古遗址中采集了七个样本，这些样本的年代测定结果显示，其年代大约在8100至2500年前。这些样本属于一个同质人群，其中约三分之二的血统与南非狩猎采集者有关，其余部分则来自东非狩猎采集者。因此，南非狩猎采集者的血统在过去曾分布于非洲大陆更广阔的区域，这使得我们很难确定这个古代人群的起源地。

The second surprise was our discovery that some of our ancient African forager population samples shared ancestry from both South African Forager lineages and East African Forager lineages. Today, South African Forager lineages are essentially entirely restricted to southernmost Africa, where they form an important part of the ancestry of nearly all of the populations that use languages with clicks in them, and where they contribute almost all the ancestry of present-day San foragers as well as the ancient forager genomes we generated from southern Africa. But our ancient samples show that the term “South African Forager” may be misleading about where the ancestral population of this group arose. Two approximately fourteen-hundred-year-old individuals from Zanzibar and Pemba islands off the coast of Tanzania—an island chain that separated from the mainland approximately ten thousand years ago as sea levels rose and thus plausibly harbors isolated descendants of a forager population that lived in East Africa around that time⁴⁰—were a mixture of approximately one-third South African Forager–related ancestry and the remainder East African Forager ancestry.⁴¹ A series of seven samples from three different archaeological sites in Malawi in south-central Africa, which we dated to between about eighty-one hundred and twenty-five hundred years ago, were part of a homogeneous population that harbored about two-thirds South African Forager–related ancestry and the remainder East African Forager ancestry. So South African Forager ancestry was in the past distributed over a much broader swath of the continent, making it hard to know where this ancient population originated.

古DNA研究告诉我们，现代非洲的历史根植于远古时期的人口分离与融合，甚至早于农业的出现。因此，正如非洲大陆幅员辽阔、地貌多样以及人类在此繁衍生息的悠久历史所预示的那样，非洲的人类历史在各个层面、各个时期都错综复杂。古DNA研究在非洲的进展才刚刚起步。未来几年，非洲将全面融入古DNA研究，来自更多地点、更久远年代的遗骸数据也将陆续到来。这些数据必将改变并澄清我们对非洲远古历史的认知。

Ancient DNA is teaching us that the history of modern Africa has its roots in ancient population separations and mixtures even before the arrival of agriculture. Thus the human story in Africa is complex at all levels and at all time depths, as might be expected from the continent’s huge size, its varied landscape, and the antiquity of the presence of our species there. The ancient DNA revolution is only just getting a toehold in Africa. In the coming years, Africa will be fully included in the ancient DNA revolution, and data will arrive from remains from more locations and from deeper times. These data will surely transform and clarify our view of what happened in the deep African past.

接下来，我们该如何理解非洲的故事？

What’s Next for Understanding the African Story

非洲人口结构复杂性最引人注目的例证之一，便是非洲大陆上的自然选择模式。如今，西非裔人群镰状细胞贫血症的发病率很高，这种疾病是由一种突变引起的，该突变改变了血液中的血红蛋白——这种分子比任何其他分子都更负责将氧气输送到全身。在自然选择的压力下，这种突变在非洲的多个地区都达到了相当高的频率：远西非（例如塞内加尔）、中西非（例如尼日利亚）以及中非（这种突变由此通过与班图人扩张相关的迁徙传播到东非和南部非洲）。这种突变在这些人群中频率如此之高的原因在于：如果一个人从父母一方或双方携带一个镰状细胞突变基因拷贝，就能免受疟疾的侵害。疟疾的危害极大，因此，携带一个镰状细胞突变基因拷贝的约20%的人口所获得的保护，在进化意义上与携带两个突变基因拷贝并患上镰状细胞贫血症（如不治疗，会在儿童时期致命）所付出的代价相平衡。值得注意的是，这种突变在非洲的三个不同地点独立出现，这一点可以从其所在序列的差异中得知。乍一看，这似乎令人惊讶，因为人们会认为，这种突变对携带者来说如此有利，以至于一旦出现，即使邻近地区之间存在少量近亲繁殖，它也会借助自然选择的顺风，在广袤的非洲疟疾流行区迅速传播。42^类似的模式也出现在乳糖酶基因突变中，这种突变使人能够在成年后消化牛奶。北非人和西非富拉尼人的乳糖酶持续存在的遗传基础与苏丹和肯尼亚的马赛人完全不同，后者携带的是不同的突变，尽管它们位于同一个基因中。 ⁴³

Some of the most striking examples of the complexity of human population structure in Africa are the patterns of natural selection on the continent. People of West African ancestry today have a high rate of sickle cell disease, conferred by a mutation that changes the blood protein hemoglobin, the molecule that more than any other is responsible for ferrying oxygen around the body. This mutation has risen to substantial frequency under the pressure of natural selection in several places in Africa: in far West Africa (e.g., Senegal), in west-central Africa (e.g., Nigeria), and in central Africa (whence the mutation spread to eastern Africa and southern Africa via the migrations associated with the Bantu expansion). The reason this mutation has risen to such a high frequency in each of these populations is that if a person carries one copy of the mutation from either of his or her parents, it protects against the infectious disease malaria. Malaria is so dangerous that the protection provided to the approximately 20 percent of the population who carry one copy of the sickle cell mutation is balanced in evolutionary terms with the cost that the approximately 1 percent of the population has to pay in carrying two copies of the mutation and suffering from sickle cell disease, which kills in childhood without treatment. Strikingly, the mutation has arisen independently in each of three locations in Africa, which we know from the fact that the sequences on which it resides are all different. From a naive perspective this seems surprising, as one would think that a mutation like this would be so advantageous to the people who carry it that once it arose it would spread around the vast malaria zone of Africa propelled by a tailwind of natural selection if there was even a small rate of interbreeding among neighbors.⁴² A similar pattern is seen for the mutations in the lactase gene that confer an ability to digest cow’s milk into adulthood. The genetic basis for lactase persistence is completely different in North Africans and in the Fulani of West Africa than it is in the Masai of Sudan and Kenya, who carry different mutations, albeit in the same gene.⁴³

正如彼得·拉尔夫和格雷厄姆·库普所展示的那样，镰状细胞突变和使人能够消化牛奶的突变在非洲的多重起源表明，自这些突变出现以来，这些人群之间的迁徙率——即使是在撒哈拉以南非洲相距不到几千公里的地区——也一直极低。因此，进化力量传播有益突变的最有效方式往往是重新创造突变，而不是从其他人群中引入突变。 ⁴⁴过去几千年来，非洲某些地区之间有限的迁徙率导致了拉尔夫和库普所描述的非洲人口结构的“镶嵌”模式。镶嵌是一个数学术语，指的是由清晰边界划分的遗传同质区域构成的“瓷砖”景观——当邻近区域之间由于基因交流而导致的同质化过程与每个区域产生新的有利变异的过程相互竞争时，就会形成这种景观。相同镰状细胞突变的区域大小取决于其在非洲的分布情况。或者，相同的乳糖酶持续性突变的盛行反映了过去几千年来非洲邻近人群之间的基因交流速率。

As Peter Ralph and Graham Coop have shown, the multiple origins in Africa of sickle cell mutations and of mutations that allow people to digest cow’s milk imply that the rate of migration among these populations—even in parts of sub-Saharan Africa less than a couple of thousand kilometers from each other—has been extraordinarily low since the need for these mutations arose. As a result, the most efficient way for evolutionary forces to spread beneficial mutations has often been to invent mutations anew rather than to import them from other populations.⁴⁴ The limited migration rates between some regions of Africa over the last few thousand years has resulted in what Ralph and Coop have described as a “tessellated” pattern of population structure in Africa. Tessellation is a mathematical term for a landscape of tiles—regions of genetic homogeneity demarcated by sharp boundaries—that is expected to form when the process of homogenization due to gene exchanges among neighbors competes with the process of generating new advantageous variations in each region. The size of the regions where the same sickle cell mutation or same lactase-persistence mutation prevails reflects the rate of gene exchange among neighboring populations in Africa over the last thousands of years.

我们对非洲人口历史的了解仍处于起步阶段，但已然可以确定的是，这段历史错综复杂，东非狩猎采集者和南非狩猎采集者等主要族群内部的分化可以追溯到远古时期，而农业传播之后又出现了多层混杂。最终，通过获取更多来自非洲的古代DNA样本，我们将能够了解过去数万年间非洲人类的变异范围，并对人口结构进行有意义的重建。

Our understanding of African population history is still in its early stages, but it is already clear that the story is complicated, with separations within major lineages such as East African Foragers and South African Foragers dating back deep in time, and layers of mixture beyond the most recent ones that have arisen due to the spread of agriculture. Eventually, by obtaining many more samples of ancient DNA from Africa, we will be able to comprehend the range of human variation in Africa in the last tens of thousands of years and make meaningful reconstructions of population structure.

我们可以肯定的是，在非洲，如同在所有已发现古代DNA的地区一样，那种认为当今人口自中心树干分枝以来就保持不变且彼此分离的进化树模型已经失效，取而代之的是人口分离和混合的漫长循环。我们同样可以肯定的是，在非洲，如同在所有已发现古代DNA的地区一样，数据将推翻许多普遍接受的假设。这种复杂性对社会的影响，以及我们需要重新思考自身身份认同的方式，正是本书第三部分的主题。

What we can already be sure of is that in Africa, as in every region that has yielded ancient DNA, the model of an evolutionary tree in which today’s populations have remained unchanged and separate since branching from a central trunk is dead, and that instead the truth has involved great cycles of population separation and mixture. What we can be sure of, too, is that in Africa, as in every world region that has yielded ancient DNA, the data will disprove many commonly held assumptions. The implications of this complexity for society, and for the way we need to rethink who we are, is the theme of part III of this book.

第三部分

Part III

破坏性基因组

The Disruptive Genome

10

10

 

 

不平等的基因组学

The Genomics of Inequality

大混合

The Great Mixing

自1492年克里斯托弗·哥伦布抵达美洲大陆以来，美洲大陆的多元文化融合几乎立即开始。欧洲殖民者、他们的非洲奴隶以及美洲原住民，他们的祖先此前已彼此隔绝数万年。相遇后的短短几年内，他们便开始融合，形成了如今数亿人口的新族群。

The American melting pot began to swirl almost as soon as Christopher Columbus arrived in 1492. European colonists, their African slaves, and the indigenous Americans were from populations whose ancestors had been isolated from each other for tens of thousands of years. Within a few years of meeting they began mixing, founding new populations that today number in the hundreds of millions.

马丁·科尔特斯（人称“混血儿”）属于最早一批混血人群。他出生于1519年，也就是他父亲埃尔南·科尔特斯率领五百名士兵推翻统治墨西哥的阿兹特克帝国的军事行动开始后的四年内。他的母亲“拉·玛琳切”是战后被西班牙人俘虏的二十名女性之一，她最初担任翻译，后来成为埃尔南·科尔特斯的情妇。西班牙人很快创造了一个词来指代像他这样拥有欧洲和美洲原住民血统的人。“混血儿”（Mestizo）一词源于西班牙语mestizaje，在英语中意为“混血”（miscegenation）——不同“种族”类型的混合。为了维护他们在社会等级中的地位，西班牙人和葡萄牙人建立了一种种姓制度，其中纯欧洲血统的人（尤其是出生在欧洲的人）拥有最高地位，而即使只有部分非欧洲血统的人则处于较低地位。地位较低。这一体系在人口混杂的必然趋势下崩溃了；几个世纪之内，纯欧洲血统的人要么成为极少数，要么彻底消失，将权力限制在纯欧洲血统人群中已不再可行。在19世纪和20世纪初的独立运动之后，混血血统在南美洲和中美洲成为一种骄傲的象征。在墨西哥，它定义了民族认同^。

Martín Cortés “el Mestizo” belonged to one of the first of those populations. He was born within four years of the start of the 1519 military campaign in which his father, Hernán Cortés, led just five hundred soldiers to overthrow the Aztec Empire that dominated Mexico. His mother, “La Malinche,” was one of twenty female captives given over to the Spanish after a battle and she first served as an interpreter before becoming the mistress of Hernán Cortés. The Spanish quickly invented a term for the people of combined European and Native American ancestry who emerged from unions like this. “Mestizo” comes from the Spanish word mestizaje, which in English means miscegenation—the mixing of different “racial” types. To maintain their status in the social hierarchy, the Spanish and Portuguese set up a casta system in which people of entirely European ancestry (especially those born in Europe) had the highest status, while people who had even some non-European ancestry had lower status. This system collapsed under the demographic inevitability of admixture; within a few centuries people of entirely European ancestry were either an extreme minority or gone, and it was no longer feasible to limit power to those with entirely European ancestry. Following the independence movements of the nineteenth and early twentieth centuries, mixed ancestry became a source of pride in South and Central America. In Mexico, it defines national identity.¹

1492年以后，非洲人向美洲的迁徙规模与欧洲人的迁徙规模相当。据估计，总共有1200万被奴役的非洲人被迫踏上这段旅程，他们被塞进船舱，然后被拍卖。^来自西班牙、葡萄牙、法国、英国和美国的奴隶贩子通过满足殖民者对劳动力的需求而暴富。非洲奴隶在秘鲁和墨西哥的银矿中劳作，种植甘蔗等作物，后来又种植烟草和棉花。与美洲原住民相比，非洲人受旧世界疾病的影响较小，也更容易被剥削，因为他们远离家乡，分散在不讲他们语言的人群中。由于失去了文化参照点，奴隶们几乎没有能力组织起来或进行反抗。他们中的大多数被卖到南美洲或加勒比海地区，在那里往往被折磨致死。大约5%到10%的奴隶被带到了后来成为美国的地区。自 1526 年葡萄牙商人首次有记录地贩卖奴隶以来，奴隶进口到新世界的数量不断增加，并稳定在每年约 75,000 人，直到跨大西洋奴隶贸易被取缔——1807 年在英国殖民地，1808 年在美国，1850 年在巴西。

Migration of Africans to the Americas after 1492 occurred on a similar scale as migration of Europeans. All told, an estimated twelve million enslaved Africans were forced to make the journey, jammed into the holds of ships before being sold at auction.² Slave traders from Spain, Portugal, France, Britain, and the United States made great fortunes by satisfying the colonialists’ need for manual labor. African slaves worked in the silver mines of Peru and Mexico and raised crops such as sugarcane and eventually tobacco and cotton. Africans were less affected by Old World diseases than Native Americans and easier to exploit than indigenous people, as they were far from home and scattered among a population that did not speak their languages. Deprived of their cultural points of reference, slaves had little ability to organize or resist. Most were sold in South America or the Caribbean, where they were often worked to death. Around 5 to 10 percent were brought to what became the United States. Following the first recorded sale of slaves by Portuguese traders in 1526, the rate of importation into the New World increased, plateauing at around seventy-five thousand per year until the trans-Atlantic slave trade was outlawed—in the British colonies in 1807, in the United States in 1808, and in Brazil in 1850.

如今，美洲有数亿人拥有非洲血统，其中巴西、加勒比海地区和美国的人口最多。美洲三大族群——欧洲人、原住民和撒哈拉以南非洲人——的融合始于近五百年前，至今仍在继续。即使在欧洲裔美国人仍占多数的美国，非裔美国人和拉丁裔美国人也占总人口的三分之一左右。这些混血族群中的几乎所有人，其基因组中都包含大量来自生活在不到二十代之前、居住在不同大陆的祖先的基因。一小部分欧洲裔美国人也拥有大量的非洲或美洲原住民血统，这是那些成功“冒充”白人融入主流社会的人留下的遗产^。3

Today there are hundreds of millions of people in the Americas with African ancestry, the largest numbers in Brazil, the Caribbean, and the United States. The mixing of three highly divergent populations in the Americas—Europeans, indigenous people, and sub-Saharan Africans—that began almost five hundred years ago continues to this day. Even in the United States, where European Americans are still in the majority, African Americans and Latinos comprise around a third of the population. Nearly all individuals from these mixed populations derive large stretches of their genomes from ancestors who lived on different continents fewer than twenty generations ago. A small percentage of European Americans have large stretches of African or Native American DNA as well, the legacy of people who successfully “passed” themselves off into the white majority.³

1973年皮尔斯·安东尼的科幻小说《与时间赛跑》设想了一个未来：欧洲殖民主义引发的种族融合最终走向不可避免的结局，到2300年，几乎所有人类都属于“标准”人群。届时，仅剩下^六位未受种族混杂的人：一对“纯种高加索人”、一对“纯种非洲人”和一对“纯种中国人”。这些“纯种人”被寄养在人类的“动物园”中，由养父母精心培育，以便与唯一一位拥有相似血统的幸存者交配，从而维持人类的多样性。这种多样性被“标准”人群视为一种不可替代的生物资源，正濒临消失。这部小说的前提是，1492 年之后的几个世纪是我们物种历史上一个独特的同质化时期，这是一个前所未有的时期，由于跨洋旅行，以前分离的人群得以混合，这使得祖先几万年甚至几十万年都没有彼此接触的人群聚集到了一起。

A 1973 science-fiction novel, Piers Anthony’s Race Against Time, envisions a future in which the mixing of populations initiated by European colonialism reaches its inevitable conclusion, and by the year 2300 nearly all humans belong to a “Standard” population.⁴ In that year, only six unmixed people are left: one pair of “purebred Caucasians,” one pair of “purebred Africans,” and one pair of “purebred Chinese.” These “purebreds” are being raised in human zoos by foster parents and are being groomed to breed with the only remaining individual of similar ancestry to sustain humanity’s diversity, a diversity that is viewed by the “Standard” population as a resource of irreplaceable biological value on the verge of being lost. The premise of the novel is that the centuries after 1492 were a uniquely homogenizing time in the history of our species, a period of unprecedented mixing of previously separated populations enabled by transoceanic travel, which brought together groups whose ancestors had not been in contact with one another for tens or hundreds of thousands of years.

但这种前提是错误的。基因组革命表明，从人类历史的长河来看，我们并非生活在一个特殊的时代。不同族群之间的融合屡见不鲜，最终使原本差异巨大的群体——例如欧洲人、非洲人和美洲原住民——趋于同质化。在许多这样的大规模融合中，一个核心特征是：一方拥有社会权力的男性与另一方拥有社会权力的女性结合。

But this premise is mistaken. The genome revolution has shown that we are not living in particularly special times when viewed from the perspective of the great sweep of the human past. Mixtures of highly divergent groups have happened time and again, homogenizing populations just as divergent from one another as Europeans, Africans, and Native Americans. And in many of these great admixtures, a central theme has been the coupling of men with social power in one population and women from the other.

开国元勋

Founding Fathers

1787年制宪会议结束后不久，后来成为美国第三任总统的托马斯·杰斐逊便与他的奴隶萨莉·海明斯发生了性关系。杰斐逊在弗吉尼亚州拥有一座大型种植园，园内大约有40名奴隶。百分之几的人口是奴隶。5^萨莉·海明斯是一位非裔美国奴隶，她的祖父母中有三位是欧洲人。但她的母亲是非洲裔奴隶，根据弗吉尼亚州的法律，奴隶身份由母系继承。杰斐逊和海明斯一共育有六个孩子^。6

Not long after the Constitutional Convention of 1787, the man who would become the United States’ third president, Thomas Jefferson, began a sexual relationship with his slave Sally Hemings. Jefferson owned a large plantation in the state of Virginia, where some 40 percent of the population was enslaved.⁵ Sally Hemings was an African American slave with three European grandparents. But her mother’s mother was a slave of African descent, and under Virginia law the status of a slave was maternally inherited. Jefferson and Hemings had six children together.⁶

杰斐逊与海明斯的关系一直备受争议，一些人认为，作为美国启蒙运动最伟大的思想家和《独立宣言》的起草者，杰斐逊不太可能维持一个私生子家庭。然而，1998年发表的一项基因研究显示，萨莉·海明斯最小的儿子埃斯顿·海明斯·杰斐逊的父系后裔与杰斐逊叔父的父系后裔的Y染色体匹配。7^理论上，如果埃斯顿·海明斯·杰斐逊的父亲是杰斐逊的男性亲属而非他本人，那么这一基因发现就可以得到解释。但目前尚无历史证据支持这种可能性，而且海明斯的另一个儿子麦迪逊·海明斯在19世纪曾讲述过海明斯与杰斐逊的关系，这段记载可信。托马斯·杰斐逊纪念基金会在2000年的一项研究得出结论，麦迪逊·海明斯的说法极有可能属实^​​。8

The Jefferson-Hemings relationship has been disputed by some who have suggested that Jefferson—who is America’s greatest Enlightenment thinker and the author of the U.S. Declaration of Independence—would not have maintained an illegitimate family. However, a genetic study published in 1998 revealed a Y-chromosome match between the male-line descendants of Eston Hemings Jefferson, the youngest son of Sally Hemings, and the male-line descendants of Jefferson’s paternal uncle.⁷ The genetic findings could in theory be explained if a male relative of Jefferson was the father rather than Jefferson himself. But there is no historical evidence for this possibility, and there is a credible nineteenth-century account of the Hemings-Jefferson relationship from Madison Hemings, another son of Hemings. A study by the Thomas Jefferson Memorial Foundation in 2000 concluded that, with high probability, the story was true.⁸

据麦迪逊·海明斯所述，他的母亲曾有机会获得自由，因为她与杰斐逊一同前往法国，当时法国奴隶制是非法的。但她同意以奴隶的身份随杰斐逊返回美国，条件是他们的孩子最终能够获得自由。海明斯比杰斐逊小三十岁，在法国，她十四岁到十六岁之间与杰斐逊开始交往，并一直依赖着他。她还是杰斐逊妻子玛莎·伦道夫的同父异母妹妹，玛莎·伦道夫几年前因难产去世，而她的父亲与萨莉·海明斯的母亲有一段秘密关系^。

According to the account of Madison Hemings, his mother had a chance at freedom because she joined Jefferson in France, where slavery was illegal, but she agreed to return as a slave to the United States with Jefferson under the condition that their children would eventually be set free. Hemings was thirty years younger than Jefferson, and in France, where she began her relationship with him between the ages of fourteen and sixteen, she was dependent on him. She was also the half sister of Jefferson’s wife, Martha Randolph, who had died of complications of childbirth several years earlier and whose father had a secret relationship with the mother of Sally Hemings.⁹

历史学家曾试图量化这类家庭在美国的普遍程度。混血婚姻往往没有记录，即使有记录，不同州对子女的分类也各不相同。遗传学或许能对此有所帮助。尽管迄今为止，还没有人分析过非裔美国人墓地的DNA来描绘混血社群在美国的出现，但遗传学或许能提供一些线索。在美国，对当代非裔美国人的基因研究已经丰富了我们对他们的了解。马克·施赖弗 (Mark Shriver) 领导了一项 2001 年的研究，该研究分析了当代欧洲人和西非人之间频率差异极大的基因突变，以研究南卡罗来纳州的非裔美国人群体。施赖弗及其同事利用这些结果估算了数十代以前生活在欧洲的祖先比例。¹⁰比例最高的地区是内陆州府哥伦比亚，约为 18%，这一比例在美国其他州的城市中处于较低水平。他们估计，南卡罗来纳州沿海地区（包括奴隶港查尔斯顿）的欧洲血统比例约为 12%，他们认为这可能反映了奴隶输入浪潮导致非洲血统比例居高不下。他们估计，沿海海岛上的欧洲血统比例最低，约为4%，这反映了定居于此的奴隶们长期与世隔绝的历史。海岛居民是唯一仍在使用源自非洲语法的语言——格拉语——的非裔美国人，这一事实也印证了这种与世隔绝的状态。对非裔美国人和欧洲人之间频率差异极大的Y染色体和线粒体DNA类型的比较也表明，这些人群中绝大多数的欧洲血统来自男性，这是社会不平等的结果，当时混血结合主要发生在自由男性和女奴之间。 ¹¹

Historians have attempted to quantify how widespread families like these were in the United States. Mixed-ancestry unions were often unrecorded, and when they were, children were categorized in different ways by different states. Genetics can help here. Although so far no one has analyzed DNA from African American graveyards to chart the emergence of a mixed-ancestry community in the United States, genetic studies of the present-day African American population are already enriching our understanding. Mark Shriver led a 2001 study that analyzed mutations that are extremely different in frequency between present-day Europeans and West Africans in order to study the African American populations of South Carolina. Shriver and his colleagues used these results to estimate the proportion of ancestors who lived in Europe a few dozen generations earlier.¹⁰ The highest proportion, around 18 percent, is found in the inland state capital, Columbia, a percentage at the low end of the range of cities in other U.S. states. They estimated about 12 percent European ancestry along the South Carolina coast, including in the slave port of Charleston, which they thought might reflect waves of slave importation keeping the African ancestry high. They estimated the lowest proportion of European ancestry, around 4 percent, on the Sea Islands off the coast, reflecting the history of isolation of the slaves who settled there, an isolation attested to by the fact that the Sea Islanders are the only African Americans still speaking a language, Gullah, with an African-derived grammar. Comparison of Y-chromosome and mitochondrial DNA types that are highly different in frequency between African Americans and Europeans also shows that by far the majority of the European ancestry in these populations comes from males, the result of social inequality in which mixed-race couplings were primarily between free males and female slaves.¹¹

南卡罗来纳州的模式是美国整体模式的一个缩影。23andMe公司（一家提供个人祖源检测的公司）的卡塔日娜·布莱克（Katarzyna Bryc）与我合作，分析了该公司数据库中五千多名自称非裔美国人的个体，发现他们基因组中大部分区域的欧洲血统比例平均为27%，但在X染色体上仅为23%。 ¹²比较X染色体和其他染色体上的祖源比例，可以提供有关人口混合过程中男性和女性行为差异的信息，因为世界上三分之二的X染色体由女性携带，而其他染色体中只有大约一半由女性携带，因此X染色体相对而言更容易受到女性历史的影响。通过计算欧洲男性和女性祖先的比例，为了解释X染色体和常染色体之间观察到的欧洲血统差异，布莱克估算出了非裔美国人中欧洲血统的男性（38%）和女性（10%）比例。这些数字表明，欧洲裔美国男性对当今非裔美国人基因构成的贡献大约是欧洲裔美国女性的四倍。当我与社会学家奥兰多·帕特森讨论这些发现时，他指出，非裔美国人欧洲血统中来自男性的比例——如果与一半不同，则被称为“性别偏向”——在奴隶制时期必然要高得多。自20世纪中叶美国民权运动以来，文化变迁导致这种性别偏向发生逆转，黑人男性与白人女性的结合增多。如果我们对一百年前的非裔美国人骨骼进行DNA研究，完全有理由预期会发现更大的性别偏向。

The patterns in South Carolina are a microcosm of those in the United States as a whole. Katarzyna Bryc, at the personal ancestry testing company 23andMe, worked with me to analyze more than five thousand self-described African Americans in the company database, and found that the average European ancestry proportion was 27 percent in most of the genome but only 23 percent on chromosome X.¹² Comparing proportions of ancestry on chromosome X and the other chromosomes can provide information about differences in male and female behavior during population mixture, because two-thirds of X chromosomes in the world are carried in females compared to only about half of all other chromosomes, so the X chromosome is relatively more influenced by female history. By computing the proportion of European male and female ancestors that would be necessary to produce the observed difference in European ancestry between chromosome X and the autosomes, Bryc was able to estimate the separate male (38 percent) and female (10 percent) proportion of European ancestors in African Americans. These numbers imply that the contribution of European American men to the genetic makeup of the present-day African American population is about four times that of European American women. When I discussed these findings with the sociologist Orlando Patterson, he pointed out that the fraction of the European ancestry in African Americans that came from males—which if different from half is called “sex bias”—must have been far greater during the time of slavery. Since the civil rights movement in the United States in the mid-twentieth century, cultural changes have caused the sex bias to reverse, with more coupling between black men and white women. If we carried out DNA studies of African American skeletons from a hundred years ago, there is every reason to expect an even greater sex bias.

基因模式表明，托马斯·杰斐逊和萨莉·海明斯的模式被无数其他夫妇复制。虽然我们之所以了解这个故事，是因为它发生在我们附近，而且涉及名人，但我们完全有理由认为，性别歧视在我们物种的历史中扮演着核心角色。基因组革命使得我们能够测量那些我们尚无记录的时期中的性别歧视，从而开始了解不平等是如何在漫长的历史中塑造人类的。

The genetic patterns suggest that the Thomas Jefferson–Sally Hemings model was replicated countless times by other couples. While this story is one we know about because it is close to us in time and involved famous people, there is every reason to think that sex bias has been central to the history of our species. The genome revolution makes it possible to measure sex bias dating to periods for which we have no records, and thus to begin to understand how inequality may have shaped humanity in deep time.

不平等的基因组特征

The Genomic Signature of Inequality

在人类中，两性之间存在着深刻的生物学差异，这意味着一个男性在生理上能够生育的子女数量远远多于一个女性。女性孕育胎儿长达九个月，并且通常会哺乳数年，之后才会再次生育。 ¹³ 而男性则能够在生育和早期抚养每个孩子上投入的时间远少于女性，这种生物学差异的影响又因社会因素而加剧，例如在许多社会中，男性被期望承担更多责任。他们很少花时间陪伴孩子。因此，从对下一代的贡献来看，有权势的男性比有权势的女性更有可能产生更大的影响，而我们可以从基因数据中看到这一点。

In humans, the profound biological differences that exist between the sexes mean that a single male is physically capable of having far more children than is a single female. Women carry unborn children for nine months and often nurse them for several years prior to having additional children.¹³ Men, meanwhile, are able to procreate while investing far less time in the bearing and early rearing of each child, a biological difference whose effects are amplified by social factors such as the fact that in many societies, men are expected to spend little time with their children. So it is that, as measured by the contribution to the next generation, powerful men have the potential to have a far greater impact than powerful women, and we can see this in genetic data.

男性生育后代数量的巨大差异意味着，通过寻找过去男性生育子女数量差异的基因组特征，我们可以从遗传学角度深入了解整个社会（而不仅仅是男性和女性之间）的社会不平等程度。成吉思汗建立的帝国就是一个绝佳的例子，其男性后代数量的不平等似乎贯穿始终。成吉思汗统治的疆域从中国一直延伸到里海。1227年成吉思汗去世后，他的继承者，包括他的几个儿子和孙子，进一步扩张了蒙古帝国的版图——东至朝鲜半岛，西至中欧，南至西藏。蒙古人在战略要地设立了驿站，驻扎着休养的战马，从而能够在其超过八千公里的疆域内实现快速的交通运输。统一的蒙古帝国存在时间很短——例如，他们在中国建立的元朝于1368年灭亡——但他们的崛起仍然对欧亚大陆的基因产生了非凡的影响^。14

The great variability among males in the number of offspring produced means that by searching for genomic signatures of past variability in the number of children men have had, we can obtain genetic insights into the degree of social inequality in society as a whole, and not just between males and females. An extraordinary example of this is provided by the inequality in the number of male offspring that seems to have characterized the empire established by Genghis Khan, who ruled lands stretching from China to the Caspian Sea. After his death in 1227, his successors, including several of his sons and grandsons, extended the Mongol Empire even farther—to Korea in the east, to central Europe in the west, and to Tibet in the south. The Mongols maintained rested horses at strategically spaced posts, allowing rapid communication across their more than eight-thousand-kilometer span of territory. The united Mongol Empire was short-lived—for example, the Yüan dynasty they established in China fell in 1368—but their rise to power nevertheless allowed them to leave an extraordinary genetic impact on Eurasia.¹⁴

2003年，克里斯托弗·泰勒-史密斯（Christopher Tyler-Smith）领导的一项研究表明，蒙古时期少数几位权势显赫的男性如何对如今生活在东欧亚大陆的数十亿人口产生了巨大的影响。 ¹⁵他对Y染色体的研究表明，一位生活在蒙古时期的男性在其统治的疆域内留下了数百万的直系父系后裔。证据是，在蒙古帝国曾经统治的地区，约有8%的男性拥有特征性的Y染色体序列，或仅与该序列存在少量突变。泰勒-史密斯及其同事将此称为“星团”，以体现单一祖先拥有众多后裔的概念，并根据Y染色体上突变积累的估计速率，将这一谱系的创始人的年代推算在1300至700年前。这个日期与成吉思汗的日期相吻合，这表明这条成功的Y染色体可能是他的。

A 2003 study led by Christopher Tyler-Smith showed how a relatively small number of powerful males living during the Mongol period succeeded in having an outsize impact on the billions of people living in East Eurasia today.¹⁵ His study of Y chromosomes suggested that one single male who lived around the time of the Mongols left many millions of direct male-line descendants across the territory that the Mongols occupied. The evidence is that about 8 percent of males in the lands that the Mongol Empire once occupied share a characteristic Y-chromosome sequence or one differing from it by just a few mutations. Tyler-Smith and his colleagues called this a “Star Cluster” to reflect the idea of a single ancestor with many descendants, and estimated the date of the founder of this lineage to be thirteen hundred to seven hundred years ago based on the estimated rate of accumulation of mutations on the Y chromosome. The date coincides with that of Genghis Khan, suggesting that this single successful Y chromosome may have been his.

星团并非亚洲独有。遗传学家丹尼尔·布拉德莱伊和他的同事们发现了一种Y染色体类型，这种类型存在于当今两三百万人中，其祖先生活在大约一千五百年前。 ¹⁶这种类型在姓氏为奥唐奈尔（O'Donnell）的人群中尤为常见，他们是中世纪爱尔兰最强大的王室家族之一——“尼尔的后裔”——的后裔。尼尔指的是九人质尼尔，他是中世纪早期爱尔兰历史上的一位传奇将领。如果尼尔确有其人，那么他生活的年代与这种Y染色体祖先的基因型大致吻合。

Star Clusters are not limited to Asia. The geneticist Daniel Bradley and his colleagues identified a Y-chromosome type that is present in two to three million people today and derives from an ancestor who lived around fifteen hundred years ago.¹⁶ It is especially common in people with the last name O’Donnell, who descend from one of the most powerful royal families of medieval Ireland, the “Descendants of Niall”—referring to Niall of the Nine Hostages, a legendary warlord from the earliest period of medieval Irish history. If Niall actually existed, he would have lived at about the right time to match the Y-chromosome ancestor.

星团之所以引人入胜，是因为它们可以与历史人物联系起来（尽管这种联系带有推测性）。但更重要的是，星团分析能够提供关于远古时期社会结构变迁的洞见，而这些信息很难通过其他途径获得。因此，即使没有全基因组数据，Y染色体和线粒体DNA分析也能在这一领域发挥指导作用。例如，历史学家们一直争论不休的问题是：人类历史在多大程度上是由那些行为对后代产生巨大影响的个体所塑造的？星团分析能够提供关于过去不同时期权力极度不平等重要性的客观信息。

Star Clusters capture the imagination because they can be tied, albeit speculatively, to historical figures. But the more important point is that Star Cluster analysis provides insights about shifts in social structure that occurred in the deep past that are difficult to get information about in other ways. This is therefore one area in which Y-chromosome and mitochondrial DNA analysis can be instructive, even without whole-genome data. For example, a perennial debate among historians is the extent to which the human past is shaped by single individuals whose actions leave a disproportionate impact on subsequent generations. Star Cluster analysis provides objective information about the importance of extreme inequalities in power at different points in the past.

由托马斯·基维西尔德（Toomas Kivisild）和马克·斯通金（Mark Stoneking）分别领导的两项研究，比较了Y染色体序列和线粒体DNA序列的星团分析结果，并得出了一个非凡的结论。 ¹⁷通过计算序列对之间每个DNA碱基的差异数量（反映了随时间以时钟式方式积累的突变），这些研究估算了不同个体对在完全男性（Y染色体）和完全女性（线粒体DNA）谱系上拥有共同祖先的时间。

Two studies, one led by Toomas Kivisild and the other led by Mark Stoneking, have compared the results of Star Cluster analysis on Y-chromosome sequences and on mitochondrial DNA sequences and arrived at an extraordinary result.¹⁷ By counting the number of differences per DNA letter between pairs of sequences, which reflects mutations that accumulated in a clocklike way over time, these studies estimated the time since different pairs of individuals shared common ancestors on the entirely male (Y-chromosome) and entirely female (mitochondrial DNA) lineages.

在对线粒体DNA数据的分析中，所有研究都发现，当今大多数夫妇在过去一万年内（世界许多地区农业转型之后）拥有共同母系祖先的概率非常低。如果这一时期人口规模一直很大，那么这样的结果完全符合预期。但在Y染色体上，研究却发现了截然不同的模式。作者发现，东亚人、欧洲人、近东人和北非人的许多星团成员都拥有共同的男性祖先，这些祖先生活在大约五千年前^。18

In mitochondrial DNA data, all the studies found that most couples living in a population today have a very low probability of sharing a common ancestor along their entirely female line in the last ten thousand years, a period postdating the transition to agriculture in many parts of the world. This is exactly as expected if population sizes were large throughout this period. But on the Y chromosome, the studies found a pattern that was strikingly different. In East Asians, Europeans, Near Easterners, and North Africans, the authors found many Star Clusters with common male ancestors living roughly around five thousand years ago.¹⁸

大约五千年前，欧亚大陆正处于考古学家安德鲁·谢拉特所称的“第二产品革命”时期。在这一时期，人们开始发现家畜除了肉类生产之外的更多用途，例如用它们拉车、耕地，以及生产乳制品和羊毛等衣物。 ¹⁹这也恰好与青铜时代的开端相吻合。青铜时代是人类流动性和财富积累大幅提升的时期，这得益于马的驯化、车轮和轮式车辆的发明，以及铜、锡等稀有金属的积累——这些金属是青铜的原料，必须从数百甚至数千公里之外进口。Y染色体模式显示，这一时期也是不平等现象显著加剧的时期，这反映了新经济时代使得权力空前集中于极少数人手中，而这种权力集中正是在这一时期开始出现的。这一时期的强大男性对后世人民产生了非凡的影响——比以往任何时期都更为深远——有些人甚至将 DNA 留给了比成吉思汗更多的后代。

The time around five thousand years ago coincides with the period in Eurasia that the archaeologist Andrew Sherratt called the “Secondary Products Revolution,” in which people began to find many uses for domesticated animals beyond meat production, including employing them to pull carts and plows and to produce dairy products and clothing such as wool.¹⁹ This was also around the time of the onset of the Bronze Age, a period of greatly increased human mobility and wealth accumulation, facilitated by the domestication of the horse, the invention of the wheel and wheeled vehicles, and the accumulation of rare metals like copper and tin, which are the ingredients of bronze and had to be imported from hundreds or even thousands of kilometers away. The Y-chromosome patterns reveal that this was also a time of greatly increased inequality, a genetic reflection of the unprecedented concentration of power in tiny fractions of the population that began to be possible during this time due to the new economy. Powerful males in this period left an extraordinary impact on the populations that followed them—more than in any previous period—with some bequeathing DNA to more descendants today than Genghis Khan.

结合古代DNA和考古发现，我们开始逐步了解这种不平等可能意味着什么。大约五千年前，黑海和里海以北地区正值亚姆纳亚人崛起时期。正如第二部分所述，他们首次利用马匹和车轮开发开阔草原的资源。 ²⁰基因数据显示，亚姆纳亚人及其后裔取得了巨大的成功，他们在很大程度上取代了西部的北欧农民和东部的中亚狩猎采集者。 ²¹

From ancient DNA combined with archaeology, we are beginning to build a picture of what this inequality might have meant. The period around five thousand years ago north of the Black and Caspian seas corresponds to the rise of the Yamnaya, who, as discussed in part II, took advantage of horses and wheels to exploit the resources of the open steppe for the first time.²⁰ The genetic data show that the Yamnaya and their descendants were extraordinarily successful, largely displacing the farmers of northern Europe in the west and the hunter-gatherers of central Asia in the east.²¹

考古学家玛丽亚·金布塔斯认为，亚姆纳亚社会的性别歧视和阶层分化程度前所未有。亚姆纳亚人留下了巨大的土墩，其中约80%的土墩中心埋葬着男性骨骼，这些骨骼通常带有暴力伤痕，并被埋葬在令人胆寒的金属匕首和斧头之中。^金布塔斯认为，亚姆纳亚人抵达欧洲预示着权力关系的转变。两性关系。这与“旧欧洲”的衰落相吻合。根据金布塔斯的说法，“旧欧洲”是一个暴力证据很少的社会，女性在其中扮演着核心的社会角色，这一点在随处可见的维纳斯雕像中显而易见。在她的重建中，“旧欧洲”被以男性为中心的社会所取代，这不仅体现在考古发现中，也体现在以男性为中心的希腊、北欧和印度神话中，这些神话很可能是由亚姆纳亚人传播的印欧文化^。23

The archaeologist Marija Gimbutas has argued that Yamnaya society was unprecedentedly sex-biased and stratified. The Yamnaya left behind great mounds, about 80 percent of which had male skeletons at the center, often with evidence of violent injuries and buried amidst fearsome metal daggers and axes.²² Gimbutas argued that the arrival of the Yamnaya in Europe heralded a shift in the power relationships between the sexes. It coincided with the decline of “Old Europe,” which according to Gimbutas was a society with little evidence of violence, and in which females played a central social role as is apparent in the ubiquitous Venus figurines. In her reconstruction, “Old Europe” was replaced by a male-centered society, evident not only in the archaeology but also in the male-centered Greek, Norse, and Hindu mythologies of the Indo-European cultures plausibly spread by the Yamnaya.²³

任何试图描绘文字出现之前人类文化面貌的尝试都需要谨慎对待。尽管如此，古代DNA数据提供的证据表明，亚姆纳亚人确实是一个权力高度集中的社会。在少数精英男性中，亚姆纳亚人携带的Y染色体几乎全部是几种类型，这表明少数男性在传播其基因方面取得了非凡的成功。相比之下，亚姆纳亚人的线粒体DNA序列则更为多样化。 ²⁴亚姆纳亚人的后裔或其近亲将他们的Y染色体传播到欧洲和印度，这种扩张对人口的影响深远，因为他们携带的Y染色体类型在青铜时代之前的欧洲和印度并不存在，而如今在这两个地区却占据主导地位。 ²⁵

Any attempt to paint a vivid picture of what a human culture was like before the period of written texts needs to be viewed with caution. Nevertheless, ancient DNA data have provided evidence that the Yamnaya were indeed a society in which power was concentrated among a small number of elite males. The Y chromosomes that the Yamnaya carried were nearly all of a few types, which shows that a limited number of males must have been extraordinarily successful in spreading their genes. In contrast, in their mitochondrial DNA, the Yamnaya had more diverse sequences.²⁴ The descendants of the Yamnaya or their close relatives spread their Y chromosomes into Europe and India, and the demographic impact of this expansion was profound, as the Y-chromosome types they carried were absent in Europe and India before the Bronze Age but are predominant in both places today.²⁵

这次亚姆纳亚的扩张也不可能完全是友好的。显而易见，如今西欧 ²⁶和印度 ²⁷的Y染色体中，草原起源的比例远高于基因组其他部分中草原血统的比例。这种男性祖先中草原血统的显著优势表明，拥有政治或社会权力的亚姆纳亚人男性后裔，在与当地男性争夺配偶方面，比当地群体中的男性更具优势。我所知的最显著的例子来自西南欧的伊比利亚半岛，亚姆纳亚人祖先在青铜时代初期（距今约4500至4000年前）迁徙至此。丹尼尔·布拉德利实验室和我的实验室分别独立地提取了这一时期个体的古代DNA ²⁸ 。我们发现，随着草原血统的到来，大约30%的伊比利亚人口被替换。然而，Y染色体的更替更为剧烈：我们的数据显示，约90%拥有亚姆纳亚血统的男性都携带一种草原起源的Y染色体类型，这种类型在此之前在伊比利亚半岛并不存在。显然，在草原扩张的过程中，存在着极其特殊的等级制度和权力失衡。

This Yamnaya expansion also cannot have been entirely friendly, as is clear from the fact that the proportion of Y chromosomes of steppe origin in both western Europe²⁶ and in India²⁷ today is much larger than the proportion of steppe ancestry in the rest of the genome. This preponderance of male ancestry coming from the steppe implies that male descendants of the Yamnaya with political or social power were more successful at competing for local mates than men from the local groups. The most striking example I know of is from Iberia in far southwestern Europe, where Yamnaya-derived ancestry arrived at the onset of the Bronze Age between forty-five hundred and four thousand years ago. Daniel Bradley’s laboratory and my laboratory independently produced ancient DNA from individuals of this period.²⁸ We found that approximately 30 percent of the Iberian population was replaced along with the arrival of steppe ancestry. However, the replacement of Y chromosomes was much more dramatic: in our data around 90 percent of males who carry Yamnaya ancestry have a Y-chromosome type of steppe origin that was absent in Iberia prior to that time. It is clear that there were extraordinary hierarchies and imbalances in power at work in the expansions from the steppe.

星团研究主要基于Y染色体和线粒体DNA。那么，全基因组分析又能带来什么呢？当利用全基因组数据重建过去一万年间大多数农业群体的祖先人口规模时，结果显示这一时期人口持续增长，而Y染色体数据并未显示出青铜时代人口瓶颈的迹象。 ²⁹这与线粒体DNA和Y染色体的平均值预期结果相悖。相反，显然Y染色体在基因组中并非代表性区域，某些基因类型比其他基因类型更容易遗传给后代。原则上，一种可能的解释是自然选择，即某些Y染色体赋予携带者生物学优势，例如更高的生育能力。但是，这种基因模式几乎在同一时期出现在世界各地——恰逢社会阶层分化加剧的时期——这一事实太过引人注目，无法用多次独立发生的有利突变所导致的自然选择来解释。我认为更合理的解释是……一个合理的解释是，在这一时期，单身男性开始积累巨大的权力，他们不仅可以获得大量女性的青睐，还能将自身的社会声望传承给后代，确保其男性后代也能获得同样的成功。这一过程导致这些男性携带的Y染色体频率代代递增，留下了能够反映过去社会状况的基因印记。

The Star Cluster work rests on Y chromosomes and mitochondrial DNA. What can whole-genome analysis add? When whole-genome data are used to reconstruct the size of the ancestral population of most agricultural groups in the last ten thousand years, they document population growth throughout this period, with no evidence of the Bronze Age population bottlenecks detected from Y chromosomes.²⁹ This is not what one would expect from averaging the mitochondrial DNA and Y chromosomes. Instead, it is clear that the Y chromosome was a nonrepresentative part of the genome where certain genetic types were more successful at being passed down to later generations than others. In principle, one possible explanation for this is natural selection, whereby some Y chromosomes gave a biological advantage to those who carried them, such as increased fertility. But the fact that this genetic pattern manifested itself around the same time in multiple places around the world—in a period coinciding with the rise of socially stratified societies—is too striking a pattern to be explained by natural selection at multiple independently occurring advantageous mutations. I think a more plausible explanation is that in this period, it began to be possible for single males to accumulate so much power that they could not only gain access to large numbers of females, but they could also pass on their social prestige to subsequent generations and ensure that their male descendants were similarly successful. This process caused the Y chromosomes these males carried to increase in frequency generation after generation, leaving a genetic scar that speaks volumes about past societies.

也可能正是在这一时期，女性个体开始积累前所未有的权力。然而，由于生物学上女性，即使是位高权重的女性，也不可能生育数量极其庞大的子女，因此社会不平等的遗传影响更容易在父系血统中体现出来。

It is also possible that in this period, individual women began to accumulate more power than they ever had before. Yet because it is biologically impossible for a woman, even a very powerful one, to have an extremely large number of children, the genetic effects of social inequality are much easier to detect on the male line.

人口混合中的性别偏向

Sex Bias in Population Mixture

人口融合的方式多种多样，例如入侵、迁徙到彼此的家园、人口扩张到同一区域，以及贸易和文化交流。理论上，不同人口可以平等融合——例如，两个资源相当的人口和平迁徙到同一区域。但更常见的情况是，这种关系是不对称的，例如来自一个群体的男性与来自另一个群体的女性融合，这在非裔美国人的历史和亚姆纳亚人的历史中都有体现。基因组不同部分记录的男性和女性的不同历史，使得研究这种融合成为可能，从而获得有关远古文化交流的线索。

There are many ways that populations come together—for example through invasions, migrations into each other’s homelands, demographic expansion into the same territory, and trade and cultural exchange. Potentially, populations could mix as equals—for example through the overlapping of two equally resourced populations moving peaceably into the same area. But much more often there is asymmetry in the relationship, as reflected in mixture involving males from one group and females from the other, as occurred in the history of African Americans and in the history of the Yamnaya. The different histories of men and women recorded in different parts of the genome make it possible to study this mixture, and thereby to obtain clues about cultural interactions that occurred long ago.

从基因数据中可以明显看出一些性别偏见的例子，这些例子可以追溯到非常古老的时期。以非非洲裔祖先群体的形成为例。任何对非非洲裔人群的基因分析都会揭示出人口瓶颈的证据，其时间可以追溯到五万年前——也就是说，少数个体繁衍出了如今的众多后代。2009年，我与实验室的博士后研究员阿隆·凯南（Alon Keinan）合作，比较了基因变异。我们研究了X染色体（两条性染色体中较大的一条）与其他基因组区域的遗传关系。出乎意料的是，我们发现非非洲裔人群X染色体上的遗传变异远低于预期，而预期值是基于男性和女性在非非洲裔人群祖先群体形成过程中所占比例相等的假设。这种模式过于极端，无法用男性多于女性参与非非洲裔人群祖先群体形成的简单情景来解释。但我们发现，一种可以解释这种模式的情景是，在非非洲裔人群祖先群体最初分化之后，其他族群的男性基因被注入到该群体中。由于男性每两条其他染色体中就有一条X染色体，因此，男性反复迁徙会降低X染色体的多样性（意味着种群中的遗传变异会减少），使其低于基因组的其他部分，从而产生我们观察到的模式^。30

Some of the examples of sex bias evident from genetic data are truly ancient. Take for example the founding of the ancestral population of non-Africans. Any genetic analysis of non-Africans reveals evidence of a population bottleneck dating to some time before fifty thousand years ago—that is, a small number of individuals giving rise to many descendants today. In 2009, I worked with Alon Keinan, a postdoctoral scientist in my laboratory, to compare genetic variation on the X chromosome, the larger of our two sex chromosomes, to the rest of the genome. To our surprise, we found much less genetic variation in non-Africans on chromosome X than would be expected from the level of variation in the rest of the genome, assuming that males and females participated equally in the founding of the ancestral population of non-Africans. The pattern was too extreme to be explained by a simple scenario of more men than women participating in the founding of the ancestral population of non-Africans. But we discovered that one scenario that could explain the pattern is that after the initial budding off of the ancestral population of non-Africans, there was genetic input into this population from males of other groups. Since males carry one copy of chromosome X for every two copies of other chromosomes, a process of repeated waves of male immigration would decrease X-chromosome diversity (meaning that there would be less genetic variation in the population) compared to the rest of the genome, producing the pattern we observed.³⁰

这一假设的合理性源于我们对中非俾格米狩猎采集人群与其周边班图语系农业人群互动情况的了解。几千年前，班图人首次从西非中部扩张出来时，他们对其遇到的热带雨林土著狩猎采集人群产生了深远的影响。这一点从以下事实可见一斑：如今，所有俾格米人都不讲班图语以外的语言，并且都拥有相当数量的班图血统。即使在今天，班图男性与俾格米女性通婚，子女在俾格米社区长大，仍然是普遍存在的现象。 ³¹班图相关基因流入俾格米人群的浪潮，与我和基南（Keinan）之前提出的非非洲人祖先人群的情况类似。这种人类学模式的遗传后果体现在，与基因组其他部分的预期相比，俾格米人在X染色体上的遗传多样性显著降低。³²或许类似的进程也发生在非非洲人的共同历史中，这也解释了为什么在这种情况下，X 染色体的多样性相对于基因组的其他部分有所降低。

This hypothesis gains some plausibility from what we know of the interaction of central African Pygmy hunter-gatherer populations with the Bantu-speaking agriculturalist populations that surround them. When the Bantu first expanded out of west-central Africa several thousand years ago, they had a profound influence on the indigenous rainforest hunter-gatherer populations they encountered, as is evident from the fact that today no Pygmies speak a non-Bantu language and all harbor substantial Bantu-related ancestry. Even today, the overwhelming pattern is that Bantu men mix with Pygmy women and the children are raised in Pygmy communities.³¹ The waves of Bantu-related gene flow into the Pygmy population are similar to the scenario that Keinan and I had suggested for the ancestral population of non-Africans. The genetic consequence of this anthropological pattern is reflected in Pygmies having a substantially reduced degree of genetic diversity on chromosome X compared to the expectation from the rest of the genome.³² Perhaps similar processes were at work in the shared history of non-Africans, explaining the reduced X-chromosome diversity relative to the rest of the genome in that case too.

人类群体混合中存在性别偏向的证据是这种情况已变得司空见惯。在美洲混血人群中，男性血统偏向欧洲血统的现象在非裔美国人中尤为显著，但在南美洲和中美洲人群中则更为罕见，埃尔南·科尔特斯和拉·马林切的故事便印证了这一点。安德烈斯·鲁伊斯-利纳雷斯及其同事记录了哥伦比亚安蒂奥基亚地区的情况。该地区在16至19世纪相对封闭，约94%的Y染色体源自欧洲，而约90%的线粒体DNA序列则源自美洲原住民。 ³³这反映了社会对美洲原住民男性的不利选择。由于几乎所有男性血统都来自欧洲，几乎所有女性血统都来自美洲原住民，人们可能会天真地认为，如今安蒂奥基亚人的基因组血统中，欧洲血统和美洲原住民血统各占一半，但事实并非如此。实际上，安蒂奥基亚人约80%的血统来自欧洲。³⁴解释是，安蒂奥基亚岛在多代人中不断涌入男性移民。最早抵达的欧洲男性与美洲原住民女性通婚。之后又有更多欧洲男性移民到来。随着欧洲男性移民潮的反复涌入，除线粒体DNA外，基因组中所有区域的欧洲血统比例持续增加，因为线粒体DNA完全由女性遗传给下一代。

Evidence of sex bias in the mixture of human populations is becoming commonplace. The male-biased European contribution to admixed populations in the Americas is stark in African Americans, but it is truly extraordinary in populations in South and Central America, reflecting stories like that of Hernán Cortés and La Malinche. Andrés Ruiz-Linares and colleagues have documented how in the Antioquia region of Colombia, which was relatively isolated between the sixteenth and nineteenth centuries, about 94 percent of the Y chromosomes are European in origin, whereas about 90 percent of the mitochondrial DNA sequences are of Native American origin.³³ This reflects social selection against Native American men. Because nearly all the male ancestry comes from Europeans and nearly all the female ancestry comes from Native Americans, one might naively expect that the people of Antioquia today would derive about half their genome-wide ancestry from Europeans and half from Native Americans, but this is not the case. Instead, about 80 percent of Antioquian ancestry comes from Europeans.³⁴ The explanation is that Antioquia was flooded by male migrants over many generations. The first European men to arrive mixed with Native American women. Additional European male migrants came later. Through repeated waves of male European migration, the proportion of European ancestry kept increasing everywhere in the genome except for mitochondrial DNA, because mitochondrial DNA is passed to the next generation entirely by females.

在距今四千年至两千年前印度现代人口形成过程中，人口混合中也出现了显著的性别偏向。 ³⁵正如第二部分所述，印度传统上社会地位较高的族群往往比传统上社会地位较低的族群拥有更多与西欧亚人相关的血统， ³⁶而且这种效应具有明显的性别偏向性，因为线粒体DNA往往主要来源于本地，而Y染色体类型中与西欧亚人具有亲缘关系的比例则高得多。 ³⁷这种模式很可能反映了这样一种历史：具有西欧亚人血统的男性在种姓制度中地位更高，有时会与地位较低的女性结婚。这表明，社会地位不平等的群体曾戏剧性地融合在一起，最终形成了印度如今的遗传结构。

Massive sex bias in population mixture also occurred between four thousand and two thousand years ago during the formation of the present-day populations of India.³⁵ As discussed in part II, endogamous groups in India with traditionally higher social status tend to have more West Eurasian–related ancestry than groups with traditionally lower social status,³⁶ and the effect is highly sex-biased, as mitochondrial DNA tends to be largely of local origin, whereas a much higher proportion of Y-chromosome types have affinity to West Eurasians.³⁷ This pattern plausibly reflects a history in which males of West Eurasian–related ancestry were more highly placed in the caste system and sometimes married lower-ranking females. It speaks to a dramatic coming together of socially unequal populations to form the present genetic structure of India.

DNA 有能力颠覆其他领域的预期。然而，在这种情况下，它也揭示了性别偏向混合的一个令人惊讶的现象。如今，几乎所有太平洋岛屿居民都拥有部分来自东亚大陆的血统。正如第二部分所述，这些血统源自台湾岛的先民，他们发明了远洋航行，并利用这项技术传播了他们的人口、语言和基因。但几乎每个太平洋岛屿居民也拥有与新几内亚岛土著狩猎采集者相关的巴布亚血统。令人惊讶的是，考虑到人口扩张中的男性倾向于与当地女性混合这一普遍规律，对线粒体DNA和Y染色体的初步研究表明，如今太平洋混血人群的大部分东亚血统DNA并非来自男性祖先，而是来自女性祖先。 ³⁸

DNA has the power to overturn expectations from other fields, though, and in this case it has also revealed a surprise about sex-biased mixture. Today, almost every Pacific island population harbors some of its ancestry from people of mainland East Asian origin. As described in part II, this ancestry derives from people whose ancestors originated on Taiwan island and who invented long-distance seafaring and used it to disperse their people, language, and genes. But almost every Pacific island population also harbors Papuan ancestry related to the indigenous hunter-gatherers of the island of New Guinea. Surprisingly, in light of the theme that males from an expanding population tend to mix with local females, initial studies of mitochondrial DNA and Y chromosomes showed that the mixed populations of the Pacific today derive most of their East Asian origin DNA not from male but from female ancestors.³⁸

对此模式的一种解释是，在早期的太平洋岛屿社会中，财产通常由母系继承，而男性是岛屿间迁徙的主要人群。 ³⁹但还有另一种因素可能也促成了这一现象。正如第二部分所述，我的实验室发现，最早居住在开阔太平洋地区的人们几乎没有巴布亚血统。 ⁴⁰我们发现，后来由西向东迁徙的、具有巴布亚和东亚大陆混合血统的人群，解释了如今在偏远的太平洋地区普遍存在巴布亚血统的原因。如果这些后来迁徙而来的男性相对于先前居住在那里的居民拥有社会优势，那么这可能导致主要具有巴布亚血统的新迁徙男性与先前定居在那里的、主要具有东亚血统的女性发生通婚。

One explanation that has been suggested for this pattern is that in early Pacific island societies, property usually passed down the female line and males were the primary people who moved across islands.³⁹ But there is another process that may also have contributed. As described in part II, my laboratory showed that the first people of the open Pacific had little Papuan-related ancestry.⁴⁰ We showed that later west-to-east waves of migration of people of mixed Papuan and mainland East Asian ancestry explain the ubiquity of Papuan ancestry in the remote Pacific today. If males from this later-arriving population had social advantages relative to the previously resident population, this could have resulted in newly arriving males of primarily Papuan ancestry mixing with previously established females of primarily East Asian–related ancestry.

太平洋岛民的例子凸显了我们不能简单地假设对性别偏向事件的基因分析会符合人类学的预期。如今基因组革命已经到来，它有能力推翻长期以来的理论，因此我们需要摒弃以往那种带着强烈预设来探究人类历史的做法。为了理解我们是谁，我们需要以谦逊和开放的心态看待过去，并随时准备改变我们原有的观念，以尊重确凿数据的力量。

The Pacific islander example highlights the importance of not simply assuming that genetic analyses of sex-biased events will fulfill expectations from anthropology. Now that the genome revolution has arrived, with its power to reject long-standing theories, we need to abandon the practice of approaching questions about the human past with strong expectations. To understand who we are, we need to approach the past with humility and with an open mind, and to be ready to change our minds out of respect for the power of hard data.

不平等基因研究的未来

The Future of Genetic Studies of Inequality

目前，我们利用基因数据研究人类历史中性别偏向的方法还非常原始，令人沮丧。迄今为止，许多关于性别偏向最有趣的发现都仅仅基于基因组中的两个区域：Y染色体和线粒体DNA，而这两个区域仅反映了我们家族谱系中极小的一部分。利用基因组的这些部分研究性别偏向的人口动态，对于理解大约一万年前发生的事件几乎毫无用处，因为在那个时间尺度上，世界上所有人都源自极少数的男性和女性祖先，而这些祖先的数量太少，不足以支持对性别偏向进行统计学上精确的测量。

At the present time, our methods for using genetic data to study sex bias in human history are frustratingly primitive. Many of the most interesting findings about sex bias so far have been based on just two locations in the genome, the Y chromosome and mitochondrial DNA, which reflect only tiny fractions of our family trees. Studies of sex-biased population dynamics using these sections of the genome become nearly useless for understanding events that occurred more than around ten thousand years ago, because at that time depth, everyone in the world descends from only a small handful of male and female ancestors who are too few in number to support a statistically precise measurement of sex bias.

然而，未来对性别偏向混合的研究将充分利用全基因组的优势。全基因组研究可以将X染色体上记录的数千个独立谱系与基因组其他部分携带的数万个独立谱系进行比较。理论上，将X染色体上的遗传变异与基因组其他部分的遗传变异进行比较，应该能提供更高的统计分辨率。但尽管一些此类研究颇具启发性，其估计的准确性迄今为止却令人失望。这可能是由于强烈的自然选择作用对X染色体的影响大于其他染色体，从而使得对其模式的解读更加困难。因此，尽管许多重大的混合事件——例如欧洲草原牧民和农民的混合，或者更早的人类史前时期尼安德特人和丹尼索瓦人与现代人的混合——很可能都存在性别偏向，但目前通过比较X染色体上的祖先成分与基因组其他部分来检测这些混合事件仍然极具挑战性。⁴¹但我们目前基于X染色体精确估计性别偏倚的问题，很大程度上是技术性的，反映了现有统计技术的局限性。未来几年将开发的新方法将充分发挥X染色体与基因组其他部分进行比较的效力。我希望这些改进的方法，以及来自当时生活在种族融合时期的人们的直接古代 DNA 数据，将使我们能够对人类远古时期不平等的本质获得新的基因组学见解。

Future studies of sex-biased mixture, though, will take full advantage of the power of the whole genome. Whole-genome studies can compare the thousands of independent genealogies recorded on chromosome X to the tens of thousands of independent genealogies carried in the rest of the genome. Comparison of genetic variation on the X chromosome to genetic variation elsewhere in the genome should in theory give far more statistical resolution, but while some studies of this sort have been revealing, the accuracy of their estimates has so far been disappointing, which may be because of intense bouts of natural selection that have affected chromosome X more than other chromosomes and that make interpretations of its patterns more difficult. So while many major mixture events—such as those of steppe pastoralists and farmers in Europe, or of Neanderthals and Denisovans with modern humans further back in human prehistory—may well have been sex-biased, detecting them by comparing fractions of ancestry on chromosome X to the rest of the genome is currently challenging.⁴¹ But our present problems with making precise estimates of sex bias based on the X chromosome are to a large extent technical, reflecting the limitations of the statistical techniques currently available. New methods that will be developed over the coming years will unleash the full power of comparison of the X chromosome to the rest of the genome. I hope that these improved methods, along with direct ancient DNA data from people who lived at the times mixture was happening, will enable new genomic insights into the nature of inequality in the deep human past.

基因组证据表明，不平等——包括男女之间、同性之间权力大小差异——由来已久，鉴于当今社会不平等现象的持续存在，这令人深思。一种可能的回应是，不平等是人性的一部分，我们应该接受它。但我认为，我们应该从中汲取的教训恰恰相反。不断努力与自身的弱点——与根植于我们生物本能的社会和行为习惯——作斗争，是我们人类作为物种所具备的高尚品质之一，也是我们取得诸多胜利和成就的关键所在。不平等由来已久的证据应该激励我们以更成熟的方式应对当今的不平等，并在我们这个时代做出更好的行为。

The genomic evidence of the antiquity of inequality—between men and women, and between people of the same sex but with greater and lesser power—is sobering in light of the undeniable persistence of inequality today. One possible response might be to conclude that inequality is part of human nature and that we should just accept it. But I think the lesson is just the opposite. Constant effort to struggle against our demons—against the social and behavioral habits that are built into our biology—is one of the ennobling behaviors of which we humans as a species are capable, and which has been critical to many of our triumphs and achievements. Evidence of the antiquity of inequality should motivate us to deal in a more sophisticated way with it today, and to behave a little better in our own time.

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种族与身份的基因组学

The Genomics of Race and Identity

对生物差异的恐惧

Fear of Biological Difference

2003年我开始第一份学术工作时，我把毕生精力都押在了这样一个想法上：美洲西非人和欧洲人混居的历史或许能帮助我们找到导致健康差异的风险因素，例如前列腺癌。前列腺癌在非裔美国人中的发病率大约是欧裔美国人的1.7倍。¹^这种差异无法用不同人群的饮食和环境差异来解释，这表明遗传因素可能发挥了作用。

When I started my first academic job in 2003, I bet my career on the idea that the history of mixture of West Africans and Europeans in the Americas would make it possible to find risk factors that contribute to health disparities for diseases like prostate cancer, which occurs at about a rate 1.7 times higher in African Americans than in European Americans.¹ This particular disparity had not been possible to explain based on dietary and environmental differences across populations, suggesting that genetic factors might play a role.

如今，非裔美国人约80%的祖先来自16至19世纪被贩卖到北美的非洲奴隶。在大批非裔美国人中，基因组中任何特定位点的非洲血统比例预计都接近平均值（非洲血统比例定义为约500年前生活在西非的祖先所占的比例）。然而，如果某些前列腺癌风险因素在西非人群中的发生频率高于欧洲人群，那么患有前列腺癌的非裔美国人在这些基因变异附近区域的非洲血统比例预计会高于平均值。这一概念可用于精确定位致病基因。

African Americans today derive about 80 percent of their ancestry from enslaved Africans brought to North America between the sixteenth and nineteenth centuries. In a large group of African Americans, the proportion of African ancestry at any one location in the genome is expected to be close to the average (defining the proportion of African ancestry as the fraction of ancestors that were in West Africa before around five hundred years ago). However, if there are risk factors for prostate cancer that occur at higher frequency in West Africans than in Europeans, then African Americans with prostate cancer are expected to have inherited more African ancestry than the average in the vicinity of these genetic variations. This idea can be used to pinpoint disease genes.

为了开展这类研究，我建立了一个分子生物学实验室。我们开展了一项研究，旨在识别西非人和欧洲人之间频率不同的基因突变。我和我的同事开发了一些方法，利用这些突变的信息来确定人们基因组中哪些位置含有源自西非和欧洲祖先的DNA片段。^为了验证这些方法的有效性，我们将其应用于多种性状的研究，包括前列腺癌、子宫肌瘤、晚期肾病、多发性硬化症、白细胞计数低和2型糖尿病。

To make such studies possible, I set up a molecular biology laboratory to identify mutations that differed in frequency between West Africans and Europeans. My colleagues and I developed methods that used information from these mutations to identify where in the genome people harbor segments of DNA derived from their West African and European ancestors.² To prove that these ideas worked in practice, we applied them to many traits, including prostate cancer, uterine fibroids, late-stage kidney disease, multiple sclerosis, low white blood cell count, and type 2 diabetes.

2006年，我和我的同事将我们的方法应用于1597名患有前列腺癌的非裔美国男性，发现他们基因组中某个区域的非洲血统比例比基因组其他区域的平均水平高出约2.8%。 ³这种非洲血统比例的偶然增加概率约为千万分之一。当我们进行更深入的研究时，发现该区域至少包含七个独立的前列腺癌风险因素，所有这些因素在西非人群中的发生率均高于欧洲人群。 ⁴我们的发现可以完全解释非裔美国人前列腺癌发病率高于欧裔美国人的原因。我们可以得出这样的结论，因为那些基因组中该小区域恰好完全由欧洲血统构成的非裔美国人，其患前列腺癌的风险与随机选择的欧裔美国人大致相同。 ⁵

In 2006, my colleagues and I applied our methods to 1,597 African American men with prostate cancer, and found that in one region of the genome, they had about 2.8 percent more African ancestry than the average in the rest of their genomes.³ The odds of seeing a rise in African ancestry this large by accident were about ten million to one. When we looked in more detail, we found that this region contained at least seven independent risk factors for prostate cancer, all more common in West Africans than in Europeans.⁴ Our findings could account entirely for the higher rate of prostate cancer in African Americans than in European Americans. We could conclude this because African Americans who happen to have entirely European ancestry in this small section of their genomes had about the same risk for prostate cancer as random European Americans.⁵

2008年，我应邀在一次关于美国不同族裔群体健康差异的会议上，就我关于前列腺癌的研究工作发表了演讲。在演讲中，我试图表达我对这种科学方法的兴奋之情，以及我坚信它有助于发现其他疾病的遗传风险因素。然而，演讲结束后，一位在场的的人类学家却愤怒地质问我。她认为，通过研究“西非”或“欧洲”的DNA片段来理解不同群体间的生物学差异，我是在玩弄种族主义的把戏。她的质疑得到了其他几位与会者的附和，我在其他会议上也遇到了类似的反应。一位听过我关于类似主题演讲的法律伦理学家建议，我或许应该将非裔美国人的祖先群体称为“A群”和“B群”。但我回应说，掩盖这项研究背后的历史模型是不诚实的。我所研究的每一个数据特征都表明，这个模型在科学上是有意义的。其一，该方法能够准确估算出人类基因组中哪些位置含有来自过去二十代生活在西非或欧洲的祖先的DNA片段，这些祖先的DNA是在殖民主义和奴隶贸易造成的基因混合之前形成的。此外，该方法还能够识别出不同人群中发病频率各异的疾病真实风险因素，从而带来有望改善人类健康的发现。

In 2008, I gave a talk about my work on prostate cancer to a conference on health disparities across ethnic groups in the United States. In my talk, I tried to communicate my excitement about the scientific approach and my conviction that it could help to find genetic risk factors for other diseases. Afterward, though, I was angrily questioned by an anthropologist in the audience, who believed that by studying “West African” or “European” segments of DNA to understand biological differences between groups, I was flirting with racism. Her questions were seconded by several others, and I encountered similar responses at other meetings. A legal ethicist who heard me talk on a similar theme suggested that I might want to refer to the populations from which African Americans descend as “cluster A” and “cluster B.” But I replied that it would be dishonest to disguise the model of history that was driving this work. Every feature of the data I looked at suggested that this model was a scientifically meaningful one, providing accurate estimates of where in the genome people harbor segments of DNA from ancestors who lived in West Africa or in Europe in the last twenty generations, prior to the mixture caused by colonialism and the slave trade. It was also clear that the approach was identifying real risk factors for disease that differ in frequency across populations, leading to discoveries with the potential to improve health.

我的提问者并非极端分子，他们表达的是一种主流观点，即探索人类群体间生物差异的研究存在危险。1942年，人类学家阿什利·蒙塔古（Ashley Montagu）撰写了《^人类最危险的神话：种族谬误》（Man's Most Dangerous Myth: The Fallacy of Race），论证种族是一个社会概念，不具有生物学现实意义，并奠定了此后人类学家和许多生物学家讨论这一问题的基调。6一个常被引用的经典例子是“黑人”定义的不一致。在美国，只要有撒哈拉以南非洲血统，即使比例很小，即使肤色很浅，人们往往都被称为“黑人”。在英国，“黑人”通常指的是任何有撒哈拉以南非洲血统且肤色较深的人。而在巴西，定义又有所不同：只有完全具有非洲血统的人才能被称为“黑人”。如果“黑人”一词有这么多不一致的定义，那么“种族”又怎么可能有生物学意义呢？

Far from being extremists, my questioners were articulating a mainstream view about the danger of work exploring biological differences among human populations. In 1942, the anthropologist Ashley Montagu wrote Man’s Most Dangerous Myth: The Fallacy of Race, arguing that race is a social concept and has no biological reality, and setting the tone for how anthropologists and many biologists have discussed this issue ever since.⁶ A classic example often cited is the inconsistent definition of “black.” In the United States, people tend to be called “black” if they have sub-Saharan African ancestry—even if it is a small fraction and even if their skin color is very light. In Great Britain, “black” tends to mean anyone with sub-Saharan African ancestry who also has dark skin. In Brazil, the definition is different yet again: a person is only “black” if he or she is entirely African in ancestry. If “black” has so many inconsistent definitions, how can there be any biological meaning to “race”?

自1972年起，遗传学论证开始被纳入人类学家关于人类群体间缺乏实质性生物学差异的论断中。同年，理查德·莱温廷发表了一项关于血液中蛋白质类型变异的研究。他将分析的人群分为^七个“种族”——西欧亚人、非洲人、东亚人、南亚人、美洲原住民、大洋洲人和澳大利亚原住民——并发现，约85%的蛋白质类型变异可归因于群体和“种族”内部的变异，而只有15%可归因于群体和“种族”之间的变异。他总结道：“种族和群体之间惊人地相似，人类变异的大部分是由个体之间的差异造成的。人类种族分类没有任何社会价值，反而会破坏社会和人际关系。既然这种种族分类现在被认为几乎没有任何遗传或生物学意义，那么它就应该被摒弃。”即使从分类学角度来看，也没有任何理由继续保留它。

Beginning in 1972, genetic arguments began to be incorporated into the assertions that anthropologists were making about the lack of substantial biological differences among human populations. In that year, Richard Lewontin published a study of variation in protein types in blood.⁷ He grouped the populations he analyzed into seven “races”—West Eurasians, Africans, East Asians, South Asians, Native Americans, Oceanians, and indigenous Australians—and found that around 85 percent of variation in the protein types could be accounted for by variation within populations and “races,” and only 15 percent by variation across them. He concluded: “Races and populations are remarkably similar to each other, with the largest part by far of human variation being accounted for by the differences between individuals. Human racial classification is of no social value and is positively destructive of social and human relations. Since such racial classification is now seen to be of virtually no genetic or taxonomic significance either, no justification can be offered for its continuance.”

通过人类学家和遗传学家的合作，人们达成共识：在足够大的群体中，人类群体之间不存在足以支撑“生物种族”概念的差异。莱文廷的研究结果清楚地表明，对于绝大多数性状而言，人类群体之间的重叠程度如此之高，以至于不可能找到任何单一的生物学特征来区分任意两个群体中的人——而这正是某些人在构思“生物种族”时直觉想到的。

In this way, through the collaboration of anthropologists and geneticists, a consensus was established that there are no differences among human populations that are large enough to support the concept of “biological race.” Lewontin’s results made it clear that for the great majority of traits, human populations overlap to such a degree that it is impossible to identify a single biological trait that distinguishes people in any two groups, which is intuitively what some people think of when they conceive of “biological race.”

但许多人类学家和遗传学家的这种共识观点，似乎未经质疑地演变成一种正统观念，即人类群体间的生物学差异微乎其微，实际上应该忽略不计——而且，由于相关问题错综复杂，因此应尽可能避免对群体间生物学差异的研究。因此，一些人类学家和社会学家认为，即便出于善意，对群体间差异的遗传学研究也存在问题，也就不足为奇了。他们担心，对这类差异的研究会被用来验证那些本应被摒弃的种族概念。他们认为，这项研究正滑向一条危险的滑坡，最终会滑向过去曾被用来为奴隶贸易、将残疾人视为生物缺陷而进行绝育的优生学运动以及纳粹屠杀六百万犹太人等伪科学论证。

But this consensus view of many anthropologists and geneticists has morphed, seemingly without questioning, into an orthodoxy that the biological differences among human populations are so modest that they should in practice be ignored—and moreover, because the issues are so fraught, that study of biological differences among populations should be avoided if at all possible. It should come as no surprise, then, that some anthropologists and sociologists see genetic research into differences across populations, even if done in a well-intentioned way, as problematic. They are concerned that work on such differences will be used to validate concepts of race that should be considered discredited. They see this work as located on a slippery slope to the kinds of pseudoscientific arguments about biological difference that were used in the past to try to justify the slave trade, the eugenics movement to sterilize the disabled as biologically defective, and the Nazis’ murder of six million Jews.

这种担忧如此强烈，以至于政治学家杰奎琳·史蒂文斯甚至建议，应该禁止讨论不同人群生物学差异的研究，甚至禁止讨论此类研究的电子邮件。她还建议美国“应该颁布一项法规，禁止其工作人员或受资助者……以任何形式（包括内部文件和对其他研究的引用）发表与种族、民族、国籍或任何其他被观察或设想为可遗传的人群类别相关的遗传学声明，除非群体之间存在统计学上的显著差异，并且对这些差异的描述将对公共卫生产生明显的益处，而这些益处必须由一个常设委员会认定，此类声明必须提交该委员会并获得批准。” ⁸

The concern is so acute that the political scientist Jacqueline Stevens has even suggested that research and even emails discussing biological differences across populations should be banned, and that the United States “should issue a regulation prohibiting its staff or grantees…from publishing in any form—including internal documents and citations to other studies—claims about genetics associated with variables of race, ethnicity, nationality, or any other category of population that is observed or imagined as heritable unless statistically significant disparities between groups exist and description of these will yield clear benefits for public health, as deemed by a standing committee to which these claims must be submitted and authorized.”⁸

祖先的语言

The Language of Ancestry

但无论我们是否愿意，基因组革命都已势不可挡。它所取得的成果使得过去半个世纪以来形成的正统观念难以维系，因为这些成果揭示了不同人群之间存在显著差异的铁证。

But whether we like it or not, there is no stopping the genome revolution. The results that it is producing are making it impossible to maintain the orthodoxy established over the last half century, as they are revealing hard evidence of substantial differences across populations.

基因组革命与人类学正统观念的首次重大交锋发生在2002年。当时，马克·费尔德曼及其同事证明，通过研究基因组中足够多的位点（他们分析了377个可变位点），可以将全球人口样本中的大多数人划分成不同的群体，这些群体与美国流行的种族分类密切相关，例如“非洲裔”、“欧洲裔”、“东亚裔”、“大洋洲裔”或“美洲原住民”。 ⁹虽然费尔德曼的结论与莱文顿的结论大体一致，即他的数据也显示群体内部的变异大于群体之间的变异，但他的研究是根据突变的组合来定义群体，而不是像莱文顿那样单独研究突变。

The first major engagement between the genome revolution and anthropological orthodoxy came in 2002, when Marc Feldman and his colleagues showed that by studying enough places in the genome—they analyzed 377 variable positions—it is possible to group most people in a worldwide population sample into clusters that correlate strongly to popular categories of race in the United States: “African,” “European,” “East Asian,” “Oceanian,” or “Native American.”⁹ While Feldman’s conclusions were broadly consistent with Lewontin’s in that his data also showed more variation within groups than among them, his study defined clusters in terms of combinations of mutations instead of looking at mutations individually as Lewontin had done.

科学家们迅速做出了回应。其中一位是斯万特·帕博，八年后，他领导了对古尼安德特人和丹尼索瓦人进行全基因组测序的工作。帕博之所以参与到关于人类种群结构本质的辩论中，是因为他担任了莱比锡马克斯·普朗克进化人类学研究所的创始主任。该研究所成立于1997年，旨在使德国重返其在二战前曾占据主导地位，但由于人类学家在纳粹种族理论发展中发挥了核心作用而基本上放弃的领域。

Scientists were quick to respond. One was Svante Pääbo, who eight years later would go on to lead the work to sequence whole genomes of archaic Neanderthals and Denisovans. Pääbo came to the debate about the nature of human population structure as a founding director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, which was set up in 1997 in an effort to return Germany to a field in which it had played a leading role before the Second World War but that it had largely abandoned due to anthropologists’ central contribution to developing Nazi race theory.

帕博认真履行着他作为一家雄心勃勃的德国人类学研究所所长的道德责任，并思考人类人口结构的真相是否更接近人类学家弗兰克·利文斯顿的观点，即“没有种族，只有渐变群”——这种观点认为，人类的遗传变异表现为渐进的地理梯度，反映了邻近人群之间的通婚。 ¹⁰ 为了探索这种可能性，帕博研究人员调查了费尔德曼研究中发现的聚类是否因为所分析的人群样本并非来自世界各地而导致其界限分明。为了理解非随机抽样如何导致这一结果，我们可以以美国为例。美国拥有极其丰富的多样性，但其非裔美国人、欧裔美国人和东亚裔等群体之间的遗传差异比移民来源地更为显著，这是因为美国的移民来自世界上的特定区域。例如，在美国，大部分非洲血统来自西非的少数几个族群，^大部分欧洲血统来自西北欧，大部分亚洲血统来自东北亚。帕博的研究表明，这种非随机抽样可以解释费尔德曼及其同事观察到的一些现象。然而，后来的研究证明，非随机抽样无法解释大部分的聚类结构，因为即使在地理分布更为均匀的样本集中重复分析，仍然观察到了显著的人群聚类现象^。

Pääbo took seriously his moral responsibility as head of an ambitious German institute of anthropology, and wondered whether the truth about human population structure could be more like the anthropologist Frank Livingston’s suggestion that “there are no races, there are only clines”—a view in which human genetic variation is characterized by gradual geographic gradients that reflect interbreeding among neighbors.¹⁰ To explore this possibility, Pääbo investigated whether the clusters the Feldman study found appeared sharply defined because the analyzed populations had been sampled in a nonrandom fashion across the world. To understand how nonrandom sampling could contribute to this result, consider the United States, which harbors extraordinary diversity, but where genetic discontinuities among groups such as African Americans, European Americans, and East Asians are sharper than in the places from which immigrant populations came because the United States has drawn its immigrants from a subset of world locations. For example, in the United States, most of the African ancestry is from a handful of groups in West Africa,¹¹ most of the European ancestry is from northwest Europe, and most of the Asian ancestry is from Northeast Asia. Pääbo showed that such nonrandom sampling could account for some of the effects Feldman and colleagues observed. However, later work proved that nonrandom sampling could not account for most of the structure, as substantial clustering of human populations is observed even when repeating analyses on geographically more evenly distributed sets of samples.¹²

2003年，尼尔·里施（Neil Risch）牵头发表了一篇论文，引发了另一场热烈的讨论。里施认为，种族分组在医学研究中非常有用，不仅可以调整社会经济和文化差异，而且还与基因差异相关，而了解这些基因差异对于疾病的诊断和治疗至关重要。 ¹³ 里施的观点被镰状细胞贫血症等例子所说服，这种疾病在非裔美国人中的发病率远高于美国其他族裔。他认为，如果患者是非裔美国人，医生更有可能想到镰状细胞贫血症是合理的。

Another flurry of discussion followed a 2003 paper led by Neil Risch, who argued that racial grouping is useful in medical research, not just to adjust for socioeconomic and cultural differences, but also because it correlates with genetic differences that are important to know about when diagnosing and treating disease.¹³ Risch was convinced by examples like sickle cell disease, which occurs far more often in African Americans than in other populations in the United States. He argued that it was appropriate for doctors to be more likely to think of sickle cell disease if the patient is African American.

2005年，美国食品药品监督管理局（FDA）批准了BiDil，这是一种由两种药物组成的复方制剂，获准用于治疗非裔美国人的心力衰竭，因为数据显示它对非裔美国人比对欧裔美国人更有效，这无疑支持了这种观点。但另一方面，大卫·戈德斯坦（David Goldstein）指出，美国的种族分类对大多数生物学结果的预测能力非常弱，因此不具有长期价值。 ¹⁴他和他的同事证明，美国人口普查分类对决定药物危险反应的基因变异频率的预测能力很差。他承认，鉴于我们目前知识匮乏，依赖种族和民族类别是有用的，但据预测，未来将直接检测个人携带的突变，并完全摒弃种族分类作为制定个性化护理决策的基础。

In 2005, the U.S. Food and Drug Administration lent support to this way of thinking when it approved BiDil, a combination of two medications approved to treat heart failure in African Americans because data suggested it was more effective in African Americans than in European Americans. But on the other side of the argument, David Goldstein suggested that U.S. racial categories are so weakly predictive of most biological outcomes that they do not have long-term value.¹⁴ He and his colleagues showed that the frequencies of genetic variants that determine dangerous reactions to drugs are poorly predicted by U.S. census categories. He acknowledged that the reliance on racial and ethnic categories is useful given our poor present knowledge, but predicted that the future will involve testing individuals directly for what mutations they have, and doing away altogether with racial classification as a basis for making individualized decisions about care.

在这种争议背景下，像我这样的研究应运而生，其重点在于确定人口起源的方法，不仅包括我们祖先的起源，还包括我们基因组中特定片段的起源。人类学家杜安娜·富尔维利（Duana Fullwiley）曾撰文指出，她所谓的“混合技术”的发展以及像我这样的遗传学家所采用的“祖先”术语，是对传统生物种族观念的回归。 ¹⁵她指出，在美国，我们使用的“祖先”术语与传统的种族分类相对接近，她认为，人口遗传学界发明了一套委婉语来讨论那些曾经的禁忌话题。这种认为我们已经接受了委婉语的观点，也得到了政治光谱另一端人士的认同。在2010年我参加的一次于冷泉港实验室举行的会议上，记者尼古拉斯·韦德（Nicholas Wade）表达了他对人口遗传学界“祖先”术语的不满，他断言“种族（race）是一个完全合适的英语词汇”。

Against this backdrop of controversy emerged work like mine, focusing on methods to determine population origin not just of our ancestors but also of individual segments of our genomes. The anthropologist Duana Fullwiley has written that the development of what she calls “admixture technology” and the language of “ancestry” that geneticists like me have adopted is a reversion to traditional ideas of biological race.¹⁵ She has pointed out that in the United States, the “ancestry” terms that we use map relatively closely to traditional racial categories, and her view is that the population genetics community has invented a set of euphemisms to discuss topics that had become taboo. The belief that we have embraced euphemisms is also shared by some on the other side of the political spectrum. At a 2010 meeting I attended at Cold Spring Harbor Laboratory, the journalist Nicholas Wade described his resentment of the population genetics community’s “ancestry” terminology, asserting that “race is a perfectly good English word.”

但“祖先”并非委婉的说法，也并非“种族”的同义词。相反，这个术语的诞生源于迫切需要一种精确的语言来讨论人与人之间的基因差异，因为科学发展终于提供了检测这些差异的工具。如今，不可否认的是，不同人群在多种性状上存在着显著的平均基因差异，而“种族”一词定义模糊，且承载了太多历史包袱，因此无济于事。如果我们继续使用“种族”一词，就无法摆脱当前的争论，这场争论陷入了两种站不住脚的立场之间的争论。一方面，人们对这些差异的本质持有基于偏见且缺乏现实依据的观点。另一方面，人们则认为人群之间的任何生物学差异都微乎其微，因此在社会政策层面可以忽略不计，掩盖过去。现在是时候摆脱这种令人束手无策的错误二分法，并弄清楚基因组究竟告诉我们什么了。

But “ancestry” is not a euphemism, nor is it synonymous with “race.” Instead, the term is born of an urgent need to come up with a precise language to discuss genetic differences among people at a time when scientific developments have finally provided the tools to detect them. It is now undeniable that there are nontrivial average genetic differences across populations in multiple traits, and the race vocabulary is too ill-defined and too loaded with historical baggage to be helpful. If we continue to use it we will not be able to escape the current debate, which is mired in an argument between two indefensible positions. On the one side there are beliefs about the nature of the differences that are grounded in bigotry and have little basis in reality. On the other side there is the idea that any biological differences among populations are so modest that as a matter of social policy they can be ignored and papered over. It is time to move on from this paralyzing false dichotomy and to figure out what the genome is actually telling us.

真正的生物学差异

Real Biological Difference

我深切理解人们担心基因研究发现的群体差异会被滥用，为种族主义辩护。但正因为如此，我才更加担忧那些否认群体间在诸多性状上存在显著生物学差异的人，正把自己置于一个站不住脚的境地，这种立场终将经不起科学的冲击。过去二十年来，大多数群体遗传学家都试图避免与正统观点相悖。当被问及人类群体间是否存在生物学差异时，我们往往含糊其辞，效仿理查德·莱文顿（Richard Lewontin）的数学理论，声称同一群体内个体间的平均差异大约是群体间平均差异的六倍。我们指出，某些在不同群体间差异显著的性状（例如肤色）背后的突变并不常见，而且当我们纵观整个基因组时，会发现不同群体间突变频率的典型差异要小得多。¹⁶但这种措辞谨慎的表述故意掩盖了不同群体间生物性状存在显著平均差异的可能性。

I have deep sympathy for the concern that genetic discoveries about differences among populations may be misused to justify racism. But it is precisely because of this sympathy that I am worried that people who deny the possibility of substantial biological differences among populations across a range of traits are digging themselves into an indefensible position, one that will not survive the onslaught of science. In the last couple of decades, most population geneticists have sought to avoid contradicting the orthodoxy. When asked about the possibility of biological differences among human populations, we have tended to obfuscate, making mathematical statements in the spirit of Richard Lewontin about the average difference between individuals from within any one population being around six times greater than the average difference between populations. We point out that the mutations that underlie some traits that differ dramatically across populations—the classic example is skin color—are unusual, and that when we look across the genome it is clear that the typical differences in frequencies of mutations across populations are far less.¹⁶ But this carefully worded formulation is deliberately masking the possibility of substantial average differences in biological traits across populations.

要理解为什么遗传学家不再能与人类学家沆瀣一气，暗示人类群体之间的差异微乎其微，可以忽略不计，只需看看“基因组博主”们就知道了。自基因组革命开始以来，互联网上充斥着关于人类变异论文的讨论，一些基因组博主甚至成为了公开数据的熟练分析师。与大多数学者相比，基因组博主的政治立场偏右——Razib Khan ¹⁷和Dienekes Pontikos ¹⁸发表的文章探讨了不同人群在包括外貌和运动能力在内的性状上的平均差异。Eurogenes博客上关于“哪些古代民族传播了印欧语系”这一敏感话题的文章，有时会引发多达上千条评论。¹⁹语言学是一个高度敏感的问题^，因为正如第二部分所述，关于印欧语系扩张的叙述已被用作构建民族神话的基础，²⁰有时甚至被滥用，例如在纳粹德国发生的情况。21基因组博客作者的政治信念部分源于这样一种观点：在讨论不同人群的生物学差异时，学术界并没有秉持科学探求真理的精神。基因组博客作者乐于指出，学术界经常发表的关于不同人群性状无法区分的政治正确言论，与他们发表的论文所表明的科学发展方向相悖的观点之间存在矛盾。

To understand why it is no longer an option for geneticists to lock arms with anthropologists and imply that any differences among human populations are so modest that they can be ignored, go no further than the “genome bloggers.” Since the genome revolution began, the Internet has been alive with discussion of the papers written about human variation, and some genome bloggers have even become skilled analysts of publicly available data. Compared to most academics, the politics of genome bloggers tend to the right—Razib Khan¹⁷ and Dienekes Pontikos¹⁸ post on findings of average differences across populations in traits including physical appearance and athletic ability. The Eurogenes blog spills over with sometimes as many as one thousand comments in response to postings on the charged topic of which ancient peoples spread Indo-European languages,¹⁹ a highly sensitive issue since as discussed in part II, narratives about the expansion of Indo-European speakers have been used as a basis for building national myths,²⁰ and sometimes have been abused as happened in Nazi Germany.²¹ The genome bloggers’ political beliefs are fueled partly by the view that when it comes to discussion about biological differences across populations, the academics are not honoring the spirit of scientific truth-seeking. The genome bloggers take pleasure in pointing out contradictions between the politically correct messages academics often give about the indis​tingu​ishab​ility of traits across populations and their papers showing that this is not the way the science is heading.

我们究竟了解哪些真正的差异？我们不能否认不同人群之间存在显著的平均基因差异，这不仅体现在肤色等特征上，还体现在体型、消化淀粉或乳糖的能力、在高海拔地区呼吸的适应能力以及对特定疾病的易感性等方面。这些差异仅仅是冰山一角。我认为，我们之所以对人类群体间更多差异知之甚少，是因为尚未开展具有足够统计效力的研究来检测这些差异。正如列文廷所说，绝大多数特征的群体内变异远大于群体间的变异。这意味着在任何群体中都可能出现大多数特征值极高或极低的个体。但这并不排除不同群体间存在更为细微的平均特征差异。

What real differences do we know about? We cannot deny the existence of substantial average genetic differences across populations, not just in traits such as skin color, but also in bodily dimensions, the ability to efficiently digest starch or milk sugar, the ability to breathe easily at high altitudes, and susceptibility to particular diseases. These differences are just the beginning. I expect that the reason we don’t know about a much larger number of differences among human populations is that studies with adequate statistical power to detect them have not yet been carried out. For the great majority of traits, there is, as Lewontin said, much more variation within populations than across populations. This means that individuals with extreme high or low values of the great majority of traits can occur in any population. But it does not preclude the existence of subtler, average differences in traits across populations.

正统观点的站不住脚之处几乎随处可见。2016年，我在哈佛大学皮博迪考古与民族学博物馆聆听了生物学家小约瑟夫·L·格雷夫斯关于种族与遗传学的讲座。讲座中，格雷夫斯将已知对皮肤色素沉着有显著影响的约五种突变（这些突变在不同人群中的频率明显不同）与已知在人脑中活跃的超过一万个基因进行了比较。他认为，与色素沉着基因不同，大脑中特别活跃的基因模式肯定会在众多区域之间相互平均，一些突变会促使认知和行为特征朝一个方向发展，而另一些则会促使其朝另一个方向发展。但这种论点站不住脚，因为事实上，如果两个种群自分离以来所受到的自然选择压力不同，那么受众多突变影响的性状与受少数突变影响的性状一样，都能够造成种群间显著的平均差异。而且，我们已经知道，由众多突变塑造的性状（例如行为和认知）至少与由少数突变驱动的性状（例如肤色）一样，是自然选择的重要目标。²²目前我们所掌握的受众多突变控制的性状的最佳例子是身高。对数十万人的研究表明，身高是由基因组中数千个可变位点决定的。2012年由乔尔·赫希霍恩（Joel Hirschhorn）领导的一项分析表明，对这些位点的自然选择导致了南欧人的平均身高低于北欧人。 ²³身高并非唯一的例子。乔纳森·普里查德领导的一项研究表明，在过去大约两千年里，英国的基因变异经历了选择压力，这些变异影响了许多其他性状，包括婴儿平均头围增大和女性平均臀围增大（可能是为了适应分娩时婴儿平均头围增大的情况）^。24

The indefensibility of the orthodoxy is obvious at almost every turn. In 2016, I attended a lecture on race and genetics by the biologist Joseph L. Graves Jr. at the Peabody Museum of Archaeology and Ethnography at Harvard. At one point, Graves compared the approximately five mutations known to have large effects on skin pigmentation and that are obviously different in frequency across populations to the more than ten thousand genes known to be active in human brains. He argued that in contrast to pigmentation genes, the patterns at genes particularly active in the brain would surely average out over so many locations, with some mutations nudging cognitive and behavioral traits in one direction and some pushing in the other direction. But this argument doesn’t work, because in fact, if natural selection has exerted different pressures on two populations since they separated, traits influenced by many mutations are just as capable of achieving large average differences across populations as traits influenced by few mutations. And indeed, it is already known that traits shaped by many mutations (as is probably the case for behavior and cognition) are at least as important targets of natural selection as traits like skin color that are driven by a small number of mutations.²² The best example we currently have of a trait governed by many mutations is height. Studies in hundreds of thousands of people have shown that height is determined by thousands of variable positions across the genome. A 2012 analysis led by Joel Hirschhorn showed that natural selection on these is responsible for the shorter average height in southern Europeans compared to northern Europeans.²³ Height isn’t the only example. Jonathan Pritchard led a study showing that in the last approximately two thousand years there has been selection for genetic variations that affect many other traits in Britain, including an increase in average infant head size and an increase in average female hip size (possibly to accommodate the increased higher average infant head size during childbirth).²⁴

人们很容易认为，基因对身体尺寸的影响是一回事，而对认知和行为特征的影响则是另一回事。但这种界限早已被跨越。通常，当一个人参与疾病的基因研究时，他或她会填写一份表格，提供身高、体重和受教育年限等信息。丹尼尔·本杰明及其同事收集了超过40万名欧洲血统人士的受教育年限信息，这些人的基因组在各种疾病研究中都经过了调查。他们发现了74种基因变异，每一种都有压倒性的证据表明，即使在控制了研究人群异质性等可能存在的混杂因素之后，这些变异在受教育年限较长的人群中比在受教育年限较短的人群中更为常见。 ²⁵本杰明及其同事还表明，基因预测受教育年限的能力远非微不足道，尽管社会因素对这种行为的平均影响肯定大于基因。他们发现，在欧洲血统人群中，他们开展了这项研究，应该可以构建一个基因预测器，其中预测值最高的20%的人完成12年教育的概率为96%，而预测值最低的人完成12年教育的概率仅为37% ^。26

It is tempting to argue that genetic influence on bodily dimensions is one thing, but that cognitive and behavioral traits are another. But this line has already been crossed. Often when a person participates in a genetic study of a disease, he or she fills out a form providing information on height, weight, and number of years of education. By compiling the information on the number of years of education for over four hundred thousand people of European ancestry whose genomes have been surveyed in the course of various disease studies, Daniel Benjamin and colleagues identified seventy-four genetic variations each of which has overwhelming evidence of being more common in people with more years of education than in people with fewer years even after controlling for such possibly confounding factors as heterogeneity in the study population.²⁵ Benjamin and colleagues also showed that the power of genetics to predict number of years of education is far from trivial, even though social influences surely have a greater average influence on this behavior than genetics. They showed that in the European ancestry population in which they carried out their study, it should be possible to build a genetic predictor in which the probability of completing twelve years of education is 96 percent for the twentieth of people with the highest prediction compared to 37 percent for the lowest.²⁶

这些基因变异如何影响教育程度？人们最直接的猜测是它们直接影响学业能力，但这很可能是错误的。一项针对十多万冰岛人的研究表明，这些变异还会提高女性生育第一个孩子的年龄，而且这种影响比对受教育年限的影响更大。这些变异可能通过间接的方式发挥作用，促使人们推迟生育，从而使他们更容易完成学业。 ²⁷这表明，当我们发现影响行为的生物学差异时，它们的作用方式可能并非我们最初设想的那样。

How do these genetic variations influence educational attainment? The obvious guess is that they have a direct effect on academic abilities, but that is probably wrong. A study of more than one hundred thousand Icelanders showed that the variations also increase the age at which a woman has her first child, and that this is a more powerful effect than the one on the number of years of education. It is possible that these variations exert their effect indirectly, by nudging people to defer having children, which makes it easier for them to complete their education.²⁷ This shows that when we discover biological differences governing behavior, they may not be working in the way we naively assume.

不同人群中影响教育程度的基因突变频率的平均差异尚未确定。但一项令人警醒的发现是，冰岛老年人的基因预测受教育年限明显高于年轻人。冰岛研究的主要作者奥古斯丁·孔（ ^Augustine Kong）指出，这反映了上个世纪以来自然选择对受教育年限较高人群的不利影响，很可能是因为自然选择倾向于选择更年轻就开始生育的人群。鉴于在自然选择的压力下，一个人受教育年限的遗传基础在一个世纪内就发生了显著变化，那么这一特征在不同人群中也极有可能存在差异。

Average differences across populations in the frequencies of the mutations that affect educational attainment have not yet been identified. But a sobering finding is that older people in Iceland are systematically different from younger people in having a higher genetically predicted number of years of education.²⁸ Augustine Kong, the lead author of the Icelandic study, showed that this reflects natural selection over the last century against people with more predicted education, likely because of selection for people who began having children at a younger age. Given that the genetic underpinnings of the number of years of education a person achieves have measurably changed within a century in a single population under the pressure of natural selection, it seems highly likely that the trait differs across populations too.

没有人知道影响欧洲血统人群教育程度的基因变异如何影响非欧洲血统人群或不同社会结构人群的行为。尽管如此，如果这些突变对某一人群的行为产生影响，那么它们很可能也会对其他人群产生影响，即使这种影响会因社会背景而异。而且，教育程度作为一种特征，可能只是受遗传因素影响的众多行为特征中的冰山一角。本杰明的研究之后，已有其他研究发现了行为特征的遗传预测因子，其中包括一项研究^{（29 ）。}在超过七万名参与者中，研究人员发现了二十多个基因的突变，这些突变能够显著预测智力测试的表现^。30

No one knows how the genetic variations that influence educational attainment in people of European ancestry affect behavior in people of non-European ancestries, or in differently structured social systems. That said, it seems likely that if these mutations have an effect on behavior in one population they will do so in others, too, even if the effects differ by social context. And educational attainment as a trait is likely to be only the tip of an iceberg of behavioral traits affected by genetics. The Benjamin study has already been joined by others finding genetic predictors of behavioral traits,²⁹ including one of more than seventy thousand people that found mutations in more than twenty genes that were significantly predictive of performance on intelligence tests.³⁰

对于那些想要反驳不同人群之间可能存在足以影响人类能力或倾向的生物学差异的人来说，最自然的辩解或许是：即便存在这种差异，它们也微乎其微。这种论点认为，即使人类群体在影响认知或行为的遗传特征方面存在平均差异，但由于人群分离至今的时间尚短，因此群体间的量化差异可能微乎其微，这与列文廷的论点不谋而合，即群体间的平均遗传差异远小于个体间的平均差异。然而，这种论点也站不住脚。从共同祖先群体分化至今，不同人类群体之间的平均时间间隔——对于某些非非洲人群而言长达五万年，对于某些撒哈拉以南非洲人群而言长达二十万年甚至更久——在人类进化的时间尺度上绝非微不足道。如果身高和婴儿头围的选择能在几千年内发生，^那么认为认知或行为特征方面不存在类似的平均差异就显得牵强附会。即便我们目前尚不清楚这些差异具体是什么，我们也应该让我们的科学和社会做好准备，去面对差异的现实，而不是视而不见，假装差异无法被发现。保持沉默，暗示公众和同行不同人群之间不太可能存在显著的特征差异，这种做法是我们科学家再也无法承受的，而且实际上弊大于利。如果我们作为科学家故意回避构建一个理性的框架来讨论人类差异，我们将留下一个真空，而伪科学将会填补这个真空，其后果远比我们坦诚交流所能达到的效果要糟糕得多。

For those who wish to argue against the possibility of biological differences across populations that are substantial enough to make a difference in people’s abilities or propensities, the most natural refuge might be to make the case that even if such differences exist, they will be small. The argument would be that even if there are average differences across human populations in genetically determined traits affecting cognition or behavior, so little time has passed since the separation of populations that the quantitative differences across populations are likely to be trivially small, harkening back to Lewontin’s argument that the average genetic difference between populations is much less than the average difference between individuals. But this argument doesn’t hold up either. The average time separation between pairs of human populations since they diverged from common ancestral populations, which is up to around fifty thousand years for some pairs of non-African populations, and up to two hundred thousand years or more for some pairs of sub-Saharan African populations, is far from negligible on the time scale of human evolution. If selection on height and infant head circumference can occur within a couple of thousand years,³¹ it seems a bad bet to argue that there cannot be similar average differences in cognitive or behavioral traits. Even if we do not yet know what the differences are, we should prepare our science and our society to be able to deal with the reality of differences instead of sticking our heads in the sand and pretending that differences cannot be discovered. The approach of staying mum, of implying to the public and to colleagues that substantial differences in traits across populations are unlikely to exist, is a strategy that we scientists can no longer afford, and that in fact is positively harmful. If as scientists we willfully abstain from laying out a rational framework for discussing human differences, we will leave a vacuum that will be filled by pseudoscience, an outcome that is far worse than anything we could achieve by talking openly.

基因组革命的洞见

The Genome Revolution’s Insight

关于传统的种族社会范畴是否与有意义的生物学范畴相对应这一问题，基因组革命已经为我们提供了全新的视角，远远超越了早期研究此问题的群体遗传学家和人类学家所能掌握的信息。从这个意义上讲，基因组革命提供的数据具有潜在的解放意义，为我们提供了一个超越当前陈旧辩论框架的智识进步契机。

On the question of whether traditional social categories of race correspond to meaningful biological categories, the genome revolution has already provided us with new insights that go far beyond the information that was available to the first population geneticists and anthropologists who grappled with the issue. In this way, the data provided by the genome revolution are potentially liberating, providing an opportunity for intellectual progress beyond the current stale framing of the debate.

直到2012年，将人类基因数据解读为指向诸如“东亚人”、“高加索人”、“西非人”、“美洲原住民”和“澳大拉西亚人”等不可改变的类别似乎仍然合理，每个群体都已分离且未混合数万年。2002年由马克·费尔德曼（Marc Feldman）领导的研究得出的聚类与这些类别相对吻合，该模型似乎能够很好地描述世界许多地区（除少数例外）的变异情况。 ³² 在其他论文中，费尔德曼及其同事提出了一个模型，解释这种结构如何在人类群体中产生。他们的观点是，大约五万年前，现代人类从非洲和近东扩张，沿途留下了后代群体，这些群体又各自繁衍出新的后代群体，而如今每个地区的居民都是最初到达的现代人类的直接后裔。³³他们的“连续创始人”模型比十七至二十世纪生物种族理论家所设想的要复杂得多，但与生物种族理论家共同预测的是，人类群体建立之后，几乎不会相互混合。

As recently as 2012, it still seemed reasonable to interpret human genetic data as pointing to immutable categories such as “East Asians,” “Caucasians,” “West Africans,” “Native Americans,” and “Australasians,” with each group having been separated and unmixed for tens of thousands of years. The 2002 study led by Marc Feldman produced clusters that corresponded relatively well to these categories, and the model seemed to be doing a good job of describing variation in many parts of the world (with some exceptions).³² In other papers, Feldman and his colleagues proposed a model for how this kind of structure could arise among human populations. Their proposal was that modern humans expanding out of Africa and the Near East after around fifty thousand years ago left descendant populations along the way, which in turn budded off their own descendant populations, with the present-day inhabitants of each region being descended directly from the modern humans who first arrived.³³ Their “serial founder” model was more sophisticated than that imagined by biological race theorists in the seventeenth to twentieth centuries, but shared with it the prediction that after being established, human populations hardly mixed with each other.

但古代DNA的发现使连续奠基者模型站不住脚。我们现在知道，当今的人口结构与数千年前的人口结构截然不同。 ³⁴相反，当今世界人口是由高度分化的人群混合而成，这些人群已不再以单一形式存在——例如，古代北欧亚人，他们贡献了……现代欧洲人、美洲原住民以及近东多个古代族群的祖先中，很大一部分都源自于此^，这些古代族群彼此之间的差异，正如今天的欧洲人和东亚人之间的差异一样。 ³⁶当今大多数人口并非一万年前生活在同一地区的族群的纯粹后裔。

But ancient DNA discoveries have rendered the serial founder model untenable. We now know that the present-day structure of populations does not reflect the one that existed many thousands of years ago.³⁴ Instead, the current populations of the world are mixtures of highly divergent populations that no longer exist in unmixed form—for example, the Ancient North Eurasians, who contributed a large amount of the ancestry of present-day Europeans as well as of Native Americans,³⁵ and multiple ancient populations of the Near East, each as differentiated from the other as Europeans and East Asians are differentiated from each other today.³⁶ Most of today’s populations are not exclusive descendants of the populations that lived in the same locations ten thousand years ago.

研究发现，人类人口结构的本质并非我们之前所设想的那样，这应该给那些自以为了解人类人口差异真相，并认为种族刻板印象与事实相符的人敲响警钟。正如在古DNA革命带来一系列惊人发现之前，我们对早期人类起源的认知存在偏差一样，我们也应该对自身关于生物差异的直觉保持警惕。目前，我们尚缺乏足够的样本量来对大多数认知和行为特征进行深入研究，但相关技术已经成熟。一旦高质量的研究得以开展——无论我们是否愿意，这些研究终将在世界各地进行——它们所发现的任何基因关联都将是无可辩驳的。我们需要认真对待这些研究，并在研究成果发表后做出负责任的回应，但可以肯定的是，某些研究结果将会令我们感到意外。

The findings that the nature of human population structure is not what we assumed should serve as a warning to those who think they know that the true nature of human population differences will correspond to racial stereotypes. Just as we had an inaccurate picture of early human origins before the ancient DNA revolution unleashed an avalanche of surprises, so we should distrust the instincts that we have about biological differences. We do not yet have sufficient sample sizes to carry out compelling studies of most cognitive and behavioral traits, but the technology is now available, and once high-quality studies are performed—which they will be somewhere in the world whether we like it or not—any genetic associations they find will be undeniable. We will need to deal with these studies and react responsibly to them when they are published, but we can already be sure that we will be surprised by some of the outcomes.

不幸的是，如今出现了一批新的作家和学者，他们不仅认为存在平均的基因差异，而且还根据传统的种族刻板印象来猜测这些差异是什么。

Unfortunately, today there is a new breed of writers and scholars who argue not only that there are average genetic differences, but that they can guess what they are based on traditional racial stereotypes.

最近一位提出人类群体差异刻板印象具有遗传基础的著名论者是《纽约时报》记者尼古拉斯·韦德，他于2014年出版了《棘手的遗产：基因、种族与人类历史》一书。 ³⁷韦德报道的核心主题是学术界倾向于结盟以维护正统观念，却又被一群敢于说真话的“叛逆者”所揭露（他曾撰文揭露科学欺诈，将人类基因组计划描述为浪费公共资金的庞然大物，并抨击全基因组关联研究在寻找导致疾病风险的常见遗传变异方面的价值）。韦德的《棘手的遗产》再次延续了这一主题，暗示人类学家和遗传学家之间已经形成了一个政治正确的联盟。压制人类群体之间存在显著差异，且这些差异与传统刻板印象相符这一事实。韦德的论点有其道理——他正确地指出了学术界试图强加一种站不住脚的正统观念的问题。然而，他提出的反驳“真理”——即不仅存在实质性差异，而且这些差异很可能与传统的种族刻板印象相符——却毫无价值。韦德的书中既有引人入胜的内容，也有完全臆测的部分，所有内容都以同样的权威性和语气呈现，因此，那些接受了书中论证充分部分的读者很容易被误导，从而接受其余部分。更糟糕的是，与韦德之前的作品相比，他之前的作品中那些敢于直言的“叛逆者”都是富有创造力和成就的学者，而他却找不到任何严肃的遗传学研究来支持他的臆测。 ³⁸然而，通过赞扬那些反对这种有缺陷的正统观念的人，他错误地暗示了他们的替代理论一定是正确的。

The person who has most recently made a prominent argument that there is a genetic basis to stereotypes about differences across human populations is the New York Times journalist Nicholas Wade, who in 2014 published A Troublesome Inheritance: Genes, Race and Human History.³⁷ The abiding theme of Wade’s reporting is the propensity of academics to band together to enforce orthodoxies and to be shown up by a band of rebels speaking the truth (he has written on scientific fraud, described the Human Genome Project as a monolith wastefully spending the public’s money, and attacked the value of genome-wide association studies for finding common genetic variations contributing to risk for diseases). Wade’s Troublesome Inheritance ran with the theme again, suggesting that a politically correct alliance of anthropologists and geneticists has banded together to suppress the truth that there are significant differences among human populations and that those differences correspond to classic stereotypes. One part of the argument has something to it—Wade correctly highlights the problem of an academic community trying to enforce an implausible orthodoxy. Yet the “truth” that he puts forward in opposition, the idea that not only are there substantial differences, but that they likely correspond to traditional racial stereotypes, has no merit. Wade’s book combines compelling content with parts that are entirely speculative, presenting everything with the same authority and in the same voice, so that naive readers who accept the parts of it that are well argued are tempted to accept the rest. Worse, when compared to Wade’s previous writing, in which the rebels speaking the truth were scholars of creativity and accomplishment, he does not identify any serious scholarship in genetics supporting his speculations.³⁸ And yet by celebrating those who have opposed the flawed orthodoxy, he implies wrongly that their alternative theories must be right.

韦德着重探讨的诸多推测中，有一章专门论述了格雷戈里·科克伦、杰森·哈迪和亨利·哈彭丁于2006年发表的一篇文章。该文章指出，阿什肯纳兹犹太人的平均智商（IQ）较高（比世界平均水平高出一个标准差以上），且其诺贝尔奖获得率也远高于世界平均水平（约为世界平均水平的100倍），这可能反映了自然选择的结果。这是因为犹太人在长达千年的历史中一直从事放贷行业，而这一行业需要书写和计算能力。 ³⁹他们还指出，阿什肯纳兹犹太人中泰-萨克斯病和戈谢病的发病率很高。这两种疾病都是由影响脑细胞脂肪储存的基因突变引起的。他们假设，这些突变的发生频率上升是由于对有助于智力发展的基因变异的选择压力所致（他们认为，当这些突变只出现一个拷贝而不是两个拷贝时，它们可能是有益的）。这一论点与以下证据相矛盾：这些疾病几乎可以肯定是由随机的不幸事件造成的——例如，在中世纪人口瓶颈时期，阿什肯纳兹犹太人数量锐减，而少数拥有众多后代的个体恰好携带了这些突变基因 ⁴⁰ ——然而，韦德仍然强调了基于此的研究。这或许是对的。哈彭丁素来喜欢在缺乏证据的情况下推测不同人群行为差异的原因。在2009年“保护西方文明”会议上，他发表讲话称，撒哈拉以南非洲裔的人如果没有工作需求，就没有工作的倾向——“我从未在非洲见过有爱好的人，”他说——他认为，这是因为撒哈拉以南非洲人在过去几千年里没有像某些欧亚人那样经历那种因勤劳而产生的自然选择。 ⁴¹

As an example of the speculations to which Wade gives pride of place, one of his chapters focuses on a 2006 essay by Gregory Cochran, Jason Hardy, and Henry Harpending suggesting that the high average intelligence quotient (IQ) of Ashkenazi Jews (more than one standard deviation above the world average), and their disproportionate share of Nobel Prizes (about one hundred times the world average), might reflect natural selection due to a millennium-long history in which Jewish populations practiced moneylending, a profession that required writing and calculation.³⁹ They also pointed to the high rate in Ashkenazi Jews of Tay-Sachs disease and Gaucher disease, which are due to mutations that affect storage of fat in brain cells, and which they hypothesized rose in frequency under the pressure of selection for genetic variations contributing to intelligence (they argued that these mutations might be beneficial when they occur in one copy rather than the two needed to cause disease). This argument is contradicted by the evidence that these diseases almost certainly owe their origin to random bad luck—the fact that during the medieval population bottleneck that affected Ashkenazi Jews, the small number of individuals who had many descendants happened to carry these mutations⁴⁰—yet Wade highlights the work on the basis that it might be right. Harpending has a track record of speculating without evidence on the causes of behavioral differences among populations. In a talk he gave at a 2009 conference on “Preserving Western Civilization,” he asserted that people of sub-Saharan African ancestry have no propensity to work when they don’t have to—“I’ve never seen anyone with a hobby in Africa,” he said—because, he thought, sub-Saharan Africans have not gone through the type of natural selection for hard work in the last thousands of years that some Eurasians had.⁴¹

韦德还重点提及了经济学家格雷戈里·克拉克的著作《告别施舍》。克拉克认为，工业革命在英国早于其他地区兴起的原因在于，此前五个世纪里，英国富裕阶层的生育率远高于贫困阶层。克拉克认为，这种较高的生育率使得资本主义蓬勃发展所需的特质得以在人口中传播，例如个人主义、耐心和长时间工作的意愿。⁴²克拉克承认他无法区分基因的传递和文化的代际传承，但韦德仍然将他的论点视为遗传因素可能发挥作用的证据。

Wade also highlighted A Farewell to Alms, a book by the economist Gregory Clark suggesting that the reason the Industrial Revolution took off in Britain before it did elsewhere was the relatively high birth rate among wealthy people in Britain for the preceding five centuries compared to less wealthy people. Clark argued that this higher birth rate spread through the population the traits needed for a capitalist surge, including individualism, patience, and willingness to work long hours.⁴² Clark admits that he cannot distinguish between the transmission of genes and the transmission of culture across the generations, but Wade nevertheless takes his argument as evidence that genetics might have played a role.

我花了一些篇幅讨论韦德书中的错误，因为我觉得有必要解释一下：即便许多学者致力于维护一种站不住脚的正统观念，也不意味着所有非正统的“异端”都是正确的。然而，韦德恰恰暗示了这一点。他写道：“每个主要文明都发展出了适合自身环境和生存的制度。但这些制度虽然深受文化传统的影响，却建立在基因塑造的人类行为基石之上。当一个文明创造出一套独特的制度并延续数代时，这表明影响人类社会行为的基因中存在着一系列与之相符的变异。” ⁴³ 韦德以一种心照不宣的方式暗示，关于不同人群之间存在差异的流行种族主义观点并非毫无道理。

I have spent some space discussing errors in Wade’s book because I feel it is important to explain that just because many academics have been engaged in trying to maintain an implausible orthodoxy, it does not mean that every unorthodox “heretic” is right. And yet Wade suggests precisely this. He writes, “Each of the major civilizations has developed the institutions appropriate for its circumstances and survival. But these institutions, though heavily imbued with cultural traditions, rest on a bedrock of genetically shaped human behavior. And when a civilization produces a distinctive set of institutions that endures for many generations, that is the sign of a supporting suite of variations in the genes that influence human social behavior.”⁴³ In a written version of a nod and a wink, Wade is suggesting that popular racist ideas about the differences that exist among populations have something to them.

韦德绝非唯一一个坚信自己掌握了不同人群差异真相的人。在2010年举行的“DNA、遗传学与人类历史”会议上，我第一次见到韦德，是听到身后传来一阵窸窣声，我震惊地转过身，看到詹姆斯·沃森，他于1953年与人共同发现了DNA的结构。沃森几年前还是冷泉港实验室的主任，而这次会面正是在那里举行的。一个世纪前，该实验室是美国优生学运动的中心，它记录着许多人的性状，以指导选择性育种，并游说各州通过立法，对被认为有缺陷的人进行绝育，以对抗他们所认为的基因库退化。具有讽刺意味的是，沃森被迫从冷泉港实验室主任的职位上退休，此前他在接受英国《星期日泰晤士报》采访时表示，他对“非洲的前景感到悲观”，并补充说“我们所有的社会政策都基于这样一个事实：他们的智力与我们相同——然而所有的测试都表明并非如此。” ⁴⁴（目前尚无基因证据支持这一说法。）我在冷泉港见到沃森时，他俯身凑近我和坐在我旁边的遗传学家贝丝·夏皮罗，低声说道：“你们什么时候才能弄明白为什么犹太人比其他人聪明这么多？”然后他说，犹太人和印度婆罗门之所以成就斐然，是因为数千年来自然选择赋予了他们成为学者的基因优势。他接着低声说，就他所见，印度人也很顺从，就像他认为他们在英国殖民统治下那样，他推测这种特性是种姓制度下选择的结果。他还谈到，东亚学生往往比较循规蹈矩，这是因为古代中国社会对顺从性的选择。

Wade is far from the only person who is convinced he knows the truth about the differences among populations. At the same 2010 meeting on “DNA, Genetics, and the History of Mankind” at which I first met Wade, I heard a rustling behind my shoulder and turned with a shock to see James Watson, who in 1953 codiscovered the structure of DNA. Watson had until a few years earlier been the director of the Cold Spring Harbor Laboratory at which the meeting was held. A century ago, the laboratory was the epicenter of the eugenics movement in the United States, keeping records on traits in many people to help guide selective breeding, and lobbying for legislation that was passed in many states to sterilize people considered to be defective and to combat a perceived degradation of the gene pool. It was ironic, then, that Watson was forced to retire as head of Cold Spring Harbor after being quoted in an interview with the British Sunday Times newspaper as having said that he was “inherently gloomy about the prospect of Africa,” adding that “[all] our social policies are based on the fact that their intelligence is the same as ours—whereas all the testing says not really.”⁴⁴ (No genetic evidence for this claim exists.) When I saw Watson at Cold Spring Harbor, he leaned over and whispered to me and to the geneticist Beth Shapiro, who was sitting next to me, something to the effect of “When are you guys going to figure out why it is that you Jews are so much smarter than everyone else?” He then said that Jews and Indian Brahmins were both high achievers because of genetic advantages conferred by thousands of years of natural selection to be scholars. He went on to whisper that Indians in his experience were also servile, much like he thought they had been under British colonialism, and he speculated that this trait had come about because of selection under the caste system. He also talked about how East Asian students tended to be conformist, because of selection for conformity in ancient Chinese society.

沃森挑战权威观点的乐趣可谓传奇。他的桀骜不驯或许是他作为科学家取得成功的重要因素。但如今，这位八十二岁的老人已不再具备严谨的学术精神，剩下的只是不加任何检验地表达直觉，而这正是他研究DNA时一贯秉持的科学严谨性。

The pleasure Watson takes in challenging establishment views is legendary. His obstreperousness may have been important to his success as a scientist. But now as an eighty-two-year-old man, his intellectual rigor was gone, and what remained was a willingness to vent his gut impressions without subjecting them to any of the testing that characterized his scientific work on DNA.

现在写下这些文字，我一想到沃森、韦德，或者他们的前辈们就可能在我身后，就感到不寒而栗。科学史一次又一次地揭示了，盲目相信直觉或盲目行事是多么危险。受偏见蒙蔽——过于确信自己掌握了真理——是错误的。例如，认为太阳绕着地球转，认为人类谱系在数千万年前就与类人猿谱系分离，认为现代人类的人口结构已有五万年历史（而事实上我们知道，它是在过去五千年间通过人口混合形成的）——从所有这些错误以及更多错误中，我们应该吸取教训，不要轻信直觉或我们周围常见的刻板印象。如果说我们能确信什么，那就是无论我们自认为感知到什么差异，我们的预期很可能都是错误的。沃森、韦德和哈彭丁的言论之所以带有种族主义色彩，是因为他们先指出学术界否认了某些可能存在的差异，然后又毫无科学证据地断言^他们知道这些差异是什么，并且这些差异与长期存在的流行刻板印象相符——这种断言几乎注定是错误的。

Writing now, I shudder to think of Watson, or of Wade, or their forebears, behind my shoulder. The history of science has revealed, again and again, the danger of trusting one’s instincts or of being led astray by one’s biases—of being too convinced that one knows the truth. From the errors of thinking that the sun revolves around the earth, that the human lineage separated from the great ape lineage tens of millions of years ago, and that the present-day human population structure is fifty thousand years old whereas in fact we know that it was forged through population mixtures largely over the last five thousand years—from all of these errors and more, we should take the cautionary lesson not to trust our gut instincts or the stereotyped expectations we find around us. If we can be confident of anything, it is that whatever differences we think we perceive, our expectations are most likely wrong. What makes Watson’s and Wade’s and Harpending’s statements racist is the way they jump from the observation that the academic community is denying the possibility of differences that are plausible, to a claim with no scientific evidence⁴⁵ that they know what those differences are and also that the differences correspond to long-standing popular stereotypes—a conviction that is essentially guaranteed to be wrong.

我们目前确实无法预知不同人群间基因编码差异的性质或发展方向。例如，西非裔人群在精英短跑运动员中的比例异常高。自1980年以来，所有奥运会百米决赛的男子选手，即使是来自欧洲和美洲的选手，都拥有西非血统。 ⁴⁶对此最常被引用的遗传学假说是，由于自然选择，西非裔人群的平均短跑能力有所提升。平均值的小幅提升看似微不足道，但在能力极高的人群中却能产生巨大的影响——例如，西非裔人群平均短跑能力提升0.8个标准差，预计会导致欧洲人群中能力高于99.9999999百分位的人群比例增加百倍。但另一种解释也能预测到同样程度的影响，那就是西非裔人群的短跑能力差异更大——能力极高和极低的人数都更多。 ⁴⁷在同一平均值附近能力分布更广，且西非裔人群中高于第99.9999999百分位数的人数比例高出百倍。事实上，考虑到西非人的遗传多样性比欧洲人高出约33%，这种情况与预期完全吻合。 ⁴⁸无论这是否能解释西非人在短跑项目中的优势，对于许多生物学特征（包括认知能力）而言，撒哈拉以南非洲人中具有极端遗传预测能力的比例预计会更高。

We truly have no idea right now what the nature or direction of genetically encoded differences among populations will be. An example is the extreme overrepresentation of people of West African ancestry among elite sprinters. All the male finalists in the Olympic hundred-meter race since 1980, even those from Europe and the Americas, had recent West African ancestry.⁴⁶ The genetic hypothesis most often invoked to explain this is that there has been an upward shift in the average sprinting ability of people of West African ancestry due to natural selection. A small increase in the average might not sound like much, but it can make a big difference at the extremes of high ability—for example, a 0.8-standard-deviation increase in the average sprinting ability in West Africans would be expected to lead to a hundredfold enrichment in the proportion of people above the 99.9999999th percentile point in Europeans. But an alternative explanation that would predict the same magnitude of effect is that there is simply more variation in sprinting ability in people of West African ancestry—with more people of both very high and very low abilities.⁴⁷ A wider spread of abilities around the same mean and a hundredfold enrichment in West Africans in the proportion of people above the 99.9999999th percentile point seen in Europeans is in fact exactly what is expected given the approximately 33 percent higher genetic diversity in West Africans than in Europeans.⁴⁸ Whether or not this explains the dominance of West Africans in sprinting, for many biological traits—including cognitive ones—there is expected to be a higher proportion of sub-Saharan Africans with extreme genetically predicted abilities.

那么，我们应该如何应对未来几年基因研究很可能揭示的行为或认知特征受基因变异影响，并且这些特征在不同人群中（无论平均值还是群体内部变异）存在差异的情况呢？即便我们目前尚不清楚这些差异具体是什么，我们也需要找到一种能够适应这些差异的全新思维方式，而不是断然否认差异的存在，从而在发现差异后束手无策。

So how should we prepare for the likelihood that in the coming years, genetic studies will show that behavioral or cognitive traits are influenced by genetic variation, and that these traits will differ on average across human populations, both with regard to their average and their variation within populations? Even if we do not yet know what those differences will be, we need to come up with a new way of thinking that can accommodate such differences, rather than deny categorically that differences can exist and so find ourselves caught without a strategy once they are found.

在基因组革命之后，人们很容易接受一种新的、令人感到安慰的陈词滥调，即援引人类历史上反复的基因混合来论证群体差异毫无意义。但这种说法是错误的。如果我们随机挑选当今世界上的两个人，就会发现构成他们的许多族群谱系已经彼此隔离了足够长的时间，足以让他们之间产生显著的平均生物学差异。面对群体间不可避免的显著差异，正确的做法是认识到这些差异的存在不应影响我们的行为方式。作为一个社会，我们应该致力于赋予每个人平等的权利，无论个体之间存在何种差异。如果我们渴望尊重每一个人，无论群体内部个体之间存在多么巨大的差异，那么包容群体间那些虽小但仍然重要的平均差异也并非难事。

It would be tempting, in the wake of the genome revolution, to settle on a new comforting platitude, invoking the history of repeated admixture in the human past as an argument for population differences being meaningless. But such a statement is wrongheaded, as if we were to randomly pick two people living in the world today, we would find that many of the population lineages contributing to them have been isolated from each other for long enough that there has been ample opportunity for substantial average biological differences to arise between them. The right way to deal with the inevitable discovery of substantial differences across populations is to realize that their existence should not affect the way we conduct ourselves. As a society we should commit to according everyone equal rights despite the differences that exist among individuals. If we aspire to treat all individuals with respect regardless of the extraordinary differences that exist among individuals within a population, it should not be so much more of an effort to accommodate the smaller but still significant average differences across populations.

除了必须给予每个人平等的尊重之外，同样重要的是要记住，人类特质存在着巨大的多样性，这不仅包括认知和行为特质，还包括运动能力、动手能力以及社交互动和同理心等方面的差异。对于大多数特质而言，个体之间的差异程度取决于个体的个体差异。人类个体数量如此庞大，以至于任何群体中的任何个体都可能在任何特质上表现出色，无论其出身如何，即便特定群体由于遗传和文化因素的共同影响而具有不同的平均值。对于大多数特质而言，勤奋努力和适宜的环境足以使那些基因预测能力较低的个体在某些任务上超越基因预测能力较高的个体。鉴于人类特质的多维性、个体间的巨大差异，以及勤奋努力和后天培养在多大程度上可以弥补遗传禀赋的不足，唯一明智的做法是将每个人和每个群体都视为人类智慧的非凡体现，并给予每个人成功的机会，无论其所展现的基因倾向的平均组合如何。

Beyond the imperative to give everyone equal respect, it is also important to keep in mind that there is a great diversity of human traits, including not just cognitive and behavioral traits, but also areas of athletic ability, skill with one’s hands, and capacity for social interaction and empathy. For most traits, the degree of variation among individuals is so large that any one person in any population can excel at any trait regardless of his or her population origin, even if particular populations have different average values due to a mixture of genetic and cultural influences. For most traits, hard work and the right environment are sufficient to allow someone with a lower genetically predicted performance at some task to excel compared to people with a higher genetically predicted performance. Because of the multidimensionality of human traits, the great variation that exists among individuals, and the extent to which hard work and upbringing can compensate for genetic endowment, the only sensible approach is to celebrate every person and every population as an extraordinary realization of our human genius and to give each person every chance to succeed, regardless of the particular average combination of genetic propensities he or she happens to display.

对我而言，应对这一挑战的自然反应是借鉴男女之间生物学差异的例子。事实上，两性之间的差异比人类群体内部的差异更为深刻，反映了超过一亿年的进化和适应。男性和女性在大量的遗传物质上存在差异——男性拥有而女性没有的Y染色体，以及女性拥有而男性没有的X染色体。大多数人都认同男女之间的生物学差异是显著的，并且这些差异导致了他们在体型、体能、性格和行为等方面的平均差异，即便对于某些特定差异在多大程度上也受到社会期望和成长环境的影响仍存在疑问（例如，如今女性大量从事的许多工业和专业工作，在一个世纪前却鲜有女性涉足）。今天，我们既渴望承认生物学差异的存在，也渴望赋予每个人平等的自由和机会，无论这些差异如何。从男女之间持续存在的平均不平等现象可以看出，实现这些愿望是一个挑战，然而重要的是要包容甚至接受实际存在的差异，同时努力争取更好的结果。

For me, the natural response to the challenge is to learn from the example of the biological differences that exist between males and females. The differences between the sexes are in fact more profound than those that exist among human populations, reflecting more than a hundred million years of evolution and adaptation. Males and females differ by huge tracts of genetic material—a Y chromosome that males have and that females don’t, and a second X chromosome that females have and males don’t. Most people accept that the biological differences between males and females are profound, and that they contribute to average differences in size and physical strength as well as in temperament and behavior, even if there are questions about the extent to which particular differences are also influenced by social expectations and upbringing (for example, many of the jobs in industry and the professions that women fill in great numbers today had few women in them a century ago). Today we aspire both to recognize that biological differences exist and to accord everyone the same freedoms and opportunities regardless of them. It is clear from the abiding average inequities that persist between women and men that fulfilling these aspirations is a challenge, and yet it is important to accommodate and even embrace the real differences that exist, while at the same time struggling to get to a better place.

归根结底，种族主义真正的冒犯之处在于，以对某个群体的刻板印象来评判个人——忽略了这样一个事实：刻板印象应用于特定个体时几乎总是具有误导性的。诸如“你是黑人，你一定有音乐天赋”或“你是犹太人，你一定很聪明”之类的说法无疑非常有害。每个人都是独立的个体，拥有独特的优势和劣势，应该受到相应的尊重。假设你是一位田径队教练，一位年轻人走过来请求参加百米赛跑的选拔，而西非裔在百米赛跑项目中的统计数据显示其比例远高于其他族裔，这表明基因可能在其中发挥作用。但对于一位优秀的教练来说，种族并不重要。测试这位年轻人的短跑速度很简单——带他/她到跑道上跑一圈，用秒表计时。大多数情况下都是如此。

The real offense of racism, in the end, is to judge individuals by a supposed stereotype of their group—to ignore the fact that when applied to specific individuals, stereotypes are almost always misleading. Statements such as “You are black, you must be musical” or “You are Jewish, you must be smart” are unquestionably very harmful. Everyone is his or her own person with unique strengths and weaknesses, and should be treated as such. Suppose you are the coach of a track-and-field team, and a young person walks on and asks to try out for the hundred-meter race, in which people of West African ancestry are statistically highly overrepresented, suggesting the possibility that genetics may play a role. For a good coach, race is irrelevant. Testing the young person’s sprinting speed is simple—take him or her out to the track to run against the stopwatch. Most situations are like this.

身份认同的新基础

A New Basis for Identity

基因组革命实际上比宣扬那些常常是错误的旧观念，更能有效地帮助我们重新理解人类的差异和身份——理解我们在周围世界中的个人位置。

The genome revolution is actually a far more effective force for coming to a new understanding of human difference and identity—for understanding our own personal place in the world around us—than for promoting old beliefs that more often than not are mistaken.

要理解基因组革命如何有力地瓦解关于身份认同的旧有刻板印象并构建新的身份认同基础，不妨思考一下，它在人类历史上发现的反复混血现象是如何摧毁了几乎所有曾经用来支持生物学民族主义的论点。纳粹关于“纯粹”的印欧语系雅利安人种的意识形态，认为他们深深扎根于德国，其根源可以通过绳纹器文化的文物追溯，但这一意识形态已被一项发现彻底粉碎：使用这些文物的人群来自俄罗斯草原的大规模迁徙，而德国民族主义者会将俄罗斯草原视为其种族来源地而深恶痛绝。 ⁴⁹印度教民族主义认为，来自南亚以外的移民对印度文化没有做出重大贡献，但这一观点也受到了挑战：如今印度人大约一半的祖先来自过去五千年间来自伊朗和欧亚草原的多波大规模迁徙。 ⁵⁰ 同样，卢旺达和布隆迪的图西族人拥有西欧亚祖先的观点也站不住脚。认为胡图族人没有农民——这种观点已被纳入种族灭绝的论证中^——是无稽之谈。我们现在知道，几乎所有现存族群都是数千年乃至数万年来反复人口混合的结果。混合是人类的天性，没有任何一个族群是——也不可能——“纯粹的”。

To understand the power of the genome revolution for undermining old stereotypes about identity and building up a new basis for identity, consider how its finding of repeated mixture in human history has destroyed nearly every argument that used to be made for biologically based nationalism. The Nazi ideology of a “pure” Indo-European-speaking Aryan race with deep roots in Germany, traceable through artifacts of the Corded Ware culture, has been shattered by the finding that the people who used these artifacts came from a mass migration from the Russian steppe, a place that German nationalists would have despised as a source.⁴⁹ The Hindutva ideology that there was no major contribution to Indian culture from migrants from outside South Asia is undermined by the fact that approximately half of the ancestry of Indians today is derived from multiple waves of mass migration from Iran and the Eurasian steppe within the last five thousand years.⁵⁰ Similarly, the idea that the Tutsis in Rwanda and Burundi have ancestry from West Eurasian farmers that Hutus do not—an idea that has been incorporated into arguments for genocide⁵¹—is nonsense. We now know that nearly every group living today is the product of repeated population mixtures that have occurred over thousands and tens of thousands of years. Mixing is in human nature, and no one population is—or could be—“pure.”

非科学家群体早已意识到基因组革命在构建全新叙事方面的潜力。非裔美国人一直走在这一运动的前沿。在奴隶贸易时期，非洲人被迫背井离乡，文化被强行剥夺，导致几代人之内，他们祖先的宗教、语言和传统大多消失殆尽。1976年，亚历克斯·哈利的小说《根》通过讲述奴隶昆塔·金特及其后裔的艰辛历程，以文学的形式开始追溯失落的根源。 ⁵² 秉承这一传统，哈佛大学文学教授亨利·路易斯·盖茨也利用基因研究的潜力，帮助非裔美国人找回失落的根源。在他制作的电视系列片《美国人的面孔》及其后续的《寻找你的根源》中，他向能够追溯到十三世纪中国祖先的大提琴家马友友宣称，作为一名非裔美国人，盖茨永远无法体会那种感受，但他表明，即使对于族谱记录有限的非裔美国人来说，遗传学也能提供丰富的信息^。53

Nonscientists have already realized the potential of the genome revolution for forming new narratives. African Americans have been at the forefront of this movement. During the slave trade, Africans were uprooted and forcibly deprived of their culture, with the effect that within a few generations much of their ancestors’ religion, language, and traditions were gone. In 1976, Alex Haley’s novel Roots used literature to begin to reclaim lost roots by recounting the odyssey of the slave Kunta Kinte and his descendants.⁵² Following in this tradition, Harvard professor of literature Henry Louis Gates Jr. has capitalized on the potential of genetic studies to recover lost roots for African Americans. In his Faces of Americans television series and the Finding Your Roots series that followed it, he declares to the cellist Yo-Yo Ma, who is able to trace his ancestry back to thirteenth-century China, that Gates, as an African American, will never know how that feels, but he shows that genetics can provide richly informative insights even for African Americans with limited genealogical records.⁵³

一个名为“个人祖源检测”的新兴产业应运而生，旨在利用基因组革命的潜力，构建新的叙事基础，并将消费者的基因组与已接受检测者的基因组进行比较。盖茨制作的电视节目围绕着追溯名人嘉宾的家谱和DNA这一理念展开，运用讲述名人个人故事的文学手法，帮助观众理解基因数据的力量，从而揭示他们原本无法知晓的家族历史。例如，这些节目揭示了嘉宾之间鲜为人知的深层关系（即近几百年内拥有共同祖先）。他们还利用基因检测，不仅确定了人们祖先居住的大陆，还确定了大陆内的具体区域。

A new industry, “personal ancestry testing,” has sprung up to capitalize on the potential of the genome revolution to form the basis for new narratives and to compare the genomes of consumers to others who have already been tested. The television programs that Gates has produced have been built around the idea of tracing the genealogies and DNA of celebrity guests, using the literary device of telling the personal stories of famous people to help viewers understand the power of genetic data to reveal features of their family’s past about which they could not otherwise have been aware. For example, the programs revealed unknown deep relationships between pairs of guests on the program (shared ancestors within the last few hundred years). They also used genetic tests to determine not only the continents on which people’s ancestors lived, but also the regions within continents.

作为一个生活在美国、亲身经历过强行剥夺他人根源历史的白人，我认为每个人——尤其是非裔美国人和美洲原住民——都有权尝试利用基因数据来填补家族历史中的空白。然而，对于那些认为个人祖源检测结果具有科学权威性的人来说，必须记住，许多检测结果很容易被误解，而且很少包含科学家在初步发现中通常会附加的警告信息。

As a white person in the United States with its history of forcible deprivation of peoples of their roots, I feel that everyone—African Americans and Native Americans especially—has the right to try to use genetic data to help fill in missing pieces in his or her family history. Nevertheless, for those who assume that personal ancestry testing results have the authority of science, it is important to keep in mind that many of the results are easily misinterpreted and rarely include the warnings that scientists attach to tentative findings.

一些最好的例子来自为非裔美国人提供基因检测结果的行业。其中一家公司是African Ancestry，它为客户提供其Y染色体或线粒体DNA类型在西非哪个部落和国家最为常见的信息。这类结果很容易被过度解读，因为西非各地Y染色体和线粒体DNA类型的频率过于相似，难以做出准确的判断。例如，假设某种Y染色体类型在豪萨族群中的频率略高于邻近的约鲁巴族、门德族、富拉尼族和贝尼族群。African Ancestry在发送报告中可能会指出，一位非裔美国男性的Y染色体类型在豪萨族群中最为常见。 ⁵⁴ 但很可能，甚至极有可能，其真正的祖先并非豪萨族群，因为西非有很多部落，而且没有哪个部落对非裔美国人的非洲血统贡献超过很小一部分。⁵⁵然而，做过这些测试的人往往会带着一种感觉回来，觉得自己了解了自己的起源。遗传学家里克·基特尔斯（Rick Kittles）是一位人口遗传学家，也是非洲祖源（African Ancestry）的联合创始人，他描述了这种感觉，并断言：“我的母系血统可以追溯到尼日利亚北部，豪萨族的故乡。之后我去了尼日利亚，与当地人交谈，了解了豪萨族的文化和传统。这让我对自己是谁有了更深的认识。” ⁵⁶理论上，全基因组祖源测试比基于Y染色体和线粒体DNA的测试效力要强得多。但目前，即使是全基因组方法也不足以提供关于非裔美国人祖先在非洲居住地的高分辨率信息，部分原因是西非现代人口的数据库不够完整。还需要进行更多研究。必须采取这些措施，才能可靠地开展此类研究。

Some of the best examples come from the industry that sprang up to provide genetic results to African Americans. One company is African Ancestry, which provides customers with information on the West African tribe and country in which their Y-chromosome or mitochondrial DNA type is most common. Such results are easy to overinterpret, as the frequencies of Y-chromosome and mitochondrial DNA types are too similar across West Africa to make exact determinations with confidence. As an example, consider a Y-chromosome type that is carried slightly more often in the Hausa ethnic group than in the neighboring Yoruba, Mende, Fulani, and Beni groups. When African Ancestry sends its report, it might state that an African American man has a Y-chromosome type that is most common in the Hausa.⁵⁴ But it is quite possible and even likely that the true ancestor was not the Hausa, because there are many tribes in West Africa, and no one tribe contributed more than a modest fraction of the African ancestry of African Americans.⁵⁵ And yet people who have taken these tests often return with the impression that they know their origin. The geneticist Rick Kittles, a population geneticist who is the cofounder of African Ancestry, described this feeling, asserting, “My female line goes back to northern Nigeria, the land of the Hausa tribe. I then went to Nigeria and talked to people and learned about the Hausa’s culture and tradition. That gave me a sense about who I am.”⁵⁶ Whole-genome ancestry tests in theory have much more power than tests based on Y chromosomes and mitochondrial DNA. But at present, even whole-genome methods are not good enough to provide high-resolution information about where the ancestors of an African American person lived within Africa, in part because the databases of present-day populations in West Africa are not complete enough. Much more research needs to be done to make it possible to carry out studies like these with any reliability.

对非裔美国人来说，另一个令人沮丧的现象是，非洲奴隶抵达北美后发生的文化巨变如此巨大，以至于如今非裔美国人在祖先的非洲来源地方面几乎没有差异。来自非洲大陆不同地区的奴隶被贩卖并与其他地区的奴隶融合，结果在几代人的时间里，早期奴隶之间巨大的文化多样性和血统差异变得模糊不清，几乎难以辨认。我在2012年与卡西亚·布莱克（Kasia Bryc）合作进行的一项未发表的研究表明，非洲血统几乎完全同质化。布莱克分析了来自芝加哥、纽约、旧金山、密西西比州、北卡罗来纳州和南卡罗来纳州海岛的15000多名非裔美国人的全基因组数据，并检验了某些非裔美国人群体是否比其他群体与特定的西非人更密切相关——正如基于美国奴隶来源路线的异质性所预期的那样。57^预期存在一些差异是合理的。在四大奴隶港口中，新奥尔良的奴隶主要来自法国奴隶贩子，而巴尔的摩、萨凡纳和查尔斯顿的奴隶则主要来自英国，他们从非洲各地贩运奴隶。但我们发现，非裔美国人西非祖先的融合如此彻底，以至于我们无法从非洲大陆人口的祖先群体中检测到任何差异。只有在南卡罗来纳州附近的海岛上，我们才发现了与非洲某个特定地点存在联系的证据，具体来说，是与塞拉利昂的人民有关。塞拉利昂是格拉海岛民至今仍在使用的、带有非洲语法的语言的发源地。要真正追溯到非洲的根源，还需要对第一代被奴役的非洲人进行古代DNA研究^。58

For African Americans, another frustration may be that the cultural upheaval that occurred after African slaves arrived in North America has been so enormous that today there are few differences among African Americans with respect to the places in Africa from which their ancestors came. Africans from one part of the continent were traded around and mixed with those from another, with the result that within a few generations the great cultural diversity and variation of ancestry that existed among the first slaves were blurred to the point of unrecognizability. The nearly complete homogenization of African ancestry that occurred was evident in an unpublished study I carried out in 2012 with Kasia Bryc, who analyzed genome-wide data from more than fifteen thousand African Americans from Chicago, New York, San Francisco, Mississippi, North Carolina, and the South Carolina Sea Islands, and tested if some African American populations were more closely related to particular West Africans than others, as might be expected based on the heterogeneous supply routes for U.S. slaves.⁵⁷ It made sense to expect some differences. Of the four big slave ports, New Orleans was supplied mostly by French slave traders, whereas Baltimore, Savannah, and Charleston were supplied mostly by the British drawing from different points in Africa. But what we found is that the mixing of the West African ancestors of African Americans has been so thorough that we could not detect any differences in the African source populations for mainland populations. Only in the Sea Islands off South Carolina did we detect evidence of a particular connection to one place in Africa, in this case to people of the country of Sierra Leone, the place of origin of the language with an African grammar still spoken by Gullah Sea Islanders. It will take ancient DNA studies of first-generation enslaved Africans to actually trace roots to Africa.⁵⁸

个人祖源检测公司提供的结果有时存在问题，这并非仅限于非裔美国人。这是一个更普遍的陷阱，源于这些公司为了追求利润，会倾向于提供看似有意义的检测结果。即使是最严谨的公司也难逃此劫。2011年至2015年间，基因检测公司23andMe就曾因提供不准确的结果而备受诟病。23andMe 为客户提供了其尼安德特人血统比例的估算值，使他们能够将自身经历与一项研究联系起来——该研究表明，非非洲裔人群的基因组中约有 2% 来自尼安德特人。 ⁵⁹然而，该测试的测量结果非常不准确，因为大多数人群中尼安德特人血统比例的真实差异仅为百分之几，而该测试报告的差异却高达几个百分点。 ⁶⁰一些人兴奋地告诉我，他们的 23andMe 尼安德特人血统测试结果显示，他们的尼安德特人血统比例位居世界前几个百分点，但由于该测试的不准确性，那些 23andMe 尼安德特人血统比例如此之高的人，其尼安德特人血统比例真正高于平均水平的概率仅略高于 50%。我曾向 23andMe 团队成员提出过这个问题，甚至在 2014 年的一篇科学论文中也重点阐述了这些问题。⁶¹后来，23andMe修改了报告，不再提供这些声明。然而，该公司仍然向客户提供其携带的尼安德特人基因突变数量的排名。62^这项排名也无法提供强有力的证据，证明客户继承的尼安德特人DNA高于其所在人群的平均水平。

The problem with the results sometimes provided by personal ancestry testing companies is not limited to African Americans. It is a more general pitfall that stems from the financial incentive that such companies have to provide people with what feel like meaningful findings. This is a problem even for the most rigorous of the companies. Between 2011 and 2015, the genetic testing company 23andMe provided customers with an estimate of their proportion of Neanderthal ancestry, allowing them to make a personal connection to the research showing that non-Africans derive around 2 percent of their genomes from Neanderthals.⁵⁹ The measurement made by the test was highly inaccurate, however, since the true variation in Neanderthal proportion within most populations is only a few tenths of a percent, and the test reports variation of a few percentage points.⁶⁰ Several people have told me excitedly that their 23andMe Neanderthal testing result put them in the top few percent of people in the world in Neanderthal ancestry, but because of the test’s inaccuracies, the probability that people who got such a high 23andMe Neanderthal reading really do have more than the average proportion of Neanderthal ancestry is only slightly greater than 50/50. I raised this problem to members of the 23andMe team and even highlighted the problems in a 2014 scientific paper.⁶¹ Later, 23andMe changed its report to no longer provide these statements. However, the company continues to provide its customers with a ranking of the number of Neanderthal-derived mutations they carry.⁶² This ranking, too, does not provide strong evidence that customers have inherited more Neanderthal DNA than their population average.

并非所有家谱公司公布的结果都是不准确的，许多人从这类测试中获得了令他们满意的信息，尤其是在追溯家族谱系时，如果纸质记录中断，情况就更加复杂。例如，被收养者寻找亲生父母，或者追溯远亲关系。

Not all the findings reported by the personal ancestry companies are inaccurate, and many people have obtained what for them is satisfying information from such testing, especially when it comes to tracing genealogies where the paper trail runs cold. One example is adoptees seeking their biological parents. Another is tracking down extended families.

但就我个人而言，我并不认为这种方法令人满意。在准备写这本书的时候，我曾考虑过是否应该将我的DNA送去个人基因检测公司，还是应该像许多报道个人祖源检测领域的记者那样，在自己的实验室里进行研究，然后再描述结果。但说实话，我对此并不感兴趣。我所在的群体——德系犹太人——已经被研究得太多了。我相信我的基因组与这个群体中的其他人的基因组大同小异。我更愿意利用我所拥有的资源，对那些研究不足的人群进行基因组测序。我也担心自学的学术陷阱。我天生就对那些……抱有怀疑。他们对自己的家庭或文化过度关注，简直是太过投入。在我的实验室里，研究人员来自世界各地，我鼓励他们（虽然并非每次都能成功）选择研究其他民族的研究项目。对我而言，将基因组作为工具，通过家庭和部落等个人纽带将自己与周围的世界联系起来，这种做法显得狭隘且缺乏意义。

From my own perspective, though, I do not find this approach to be satisfying. In preparing to write this book, I considered whether I should send my DNA to a personal testing company or study it in my own lab, and then describe the results, in imitation of the approach taken by many journalists covering the field of personal ancestry testing. But honestly, I am not interested. My own group—Ashkenazi Jews—is already overstudied. I am confident that my genome will be much like that of anyone else from this population. I would much rather use any resources I have to sequence the genomes of people who are understudied. I am also worried about the intellectual pitfall of self-study. I am innately suspicious of scientists who are hyper-interested in their own family or culture. They simply care too much. In my own laboratory, there are researchers from all over the world, and I encourage them, not always successfully, to choose projects on peoples not their own. For me, the approach of using the genome as a tool to connect myself to the world around me through personal links of family and tribe seems parochial and unfulfilling.

然而，基因组革命带给我们的，是一种更为重要的认识自我的方式——一种将当今和过去人类非凡多样性铭记于心的方式。理解自我与世界之间的联系对我而言至关重要，也正是这种理解驱动着我毕生对地理、历史和生物学的兴趣。颇具讽刺意味的是，对于像我这样完全没有宗教信仰的人来说，正是《圣经》中的一个例子让我领悟到，基因组革命或许能够帮助我们解决这个关乎存在的根本问题。

What the genome revolution has given us, though, is an even more important way to come to grips with who we are—a way to hold in our minds the extraordinary human diversity that exists today and has existed in our past. The problem of understanding the connections between self and the world is a central one for me, and has driven my lifelong interest in geography, history, and biology. Ironically for a person like myself, who is not at all religious, it is an example from the Bible that provides me with insight into how the genome revolution might be able to help solve this existential problem.

每年逾越节，犹太人都会围坐在餐桌旁，讲述出埃及记的故事。逾越节对犹太人意义重大，因为它提醒他们自己在世界上的位置，并鼓励他们从中汲取教训，反思自己的行为准则。这个故事非常成功，它维系了生活在异乡的犹太人数千年的身份认同。

Every year on the holiday of Passover, Jews sit around the dinner table and recount the story of the Exodus from Egypt. The Passover holiday is important to Jews because it reminds them of their place in the world and encourages them to draw lessons about how they should behave. This narrative has been extraordinarily successful, as measured by the fact that it has sustained Jews in their identity for thousands of years as a minority living in foreign lands.

逾越节的故事始于古代以色列先祖的神话：第一代是亚伯拉罕和撒拉；第二代是以撒和利百加；第三代是雅各、利亚、拉结、辟拉和悉帕；第四代是十二个儿子（以色列各支派的祖先）和一个女儿底拿。这些人与当今庞大的人口相距甚远，似乎与当下并无直接关联。将这个古老的家族与后世众多的人们联系起来的文学手法是约瑟，雅各的儿子之一。他被兄弟们卖到埃及为奴，后来却身居要职。当饥荒席卷大地时，雅各的家人也迁徙到埃及，尽管他们之前曾得罪过约瑟，约瑟仍然接纳了他们。四百年过去了，他们的后裔呈指数级增长，最终形成了一个拥有超过六十万适龄男性和更多女性的民族。以及他们的子孙后代。在摩西的带领下，他们挣脱了压迫的枷锁，流浪数十年，制定了自己的律法。之后，他们返回了祖先的应许之地。

The Passover story begins with the myth of the patriarchs in ancient Israel: the first generation of Abraham and Sarah; the second of Isaac and Rebecca; the third of Jacob, Leah, Rachel, Bilhah, and Zilpah; and the fourth generation of twelve male children (the forefathers of the tribes of Israel) and a daughter, Dinah. These people are too removed from the huge populations of today to seem meaningfully connected to the present. The literary device that connects this ancient family to the multitudes that follow is Joseph, one of the sons of Jacob, who is sold by his brothers into slavery in Egypt, and who rises to a position of great power. When a famine strikes the land, the rest of the family also migrates to Egypt, where they are welcomed by Joseph despite the earlier crime they had committed against him. Four hundred years pass, and their descendants exponentially multiply into a nation numbering more than six hundred thousand military-age men and an even larger number of women and children. Under the leadership of Moses, they break their bonds of oppression, wander for dozens of years, and work out their code of laws. They then return to the Promised Land of their ancestors.

读完逾越节的故事后，犹太人会本能地理解，在他们数百万的族群中，彼此之间以及与过去是如何紧密相连的。这个故事让犹太人将数百万同教信徒视为直接的亲人——即使他们并不完全了解彼此之间的关系，也能给予他们同样的尊重和重视——从而打破我们从小成长的小家庭视角来看待世界的局限。

After reading the Passover story, Jews intuitively understand how within their population, numbering millions of people, they are related to each other and the past. The story allows Jews to think of those millions of coreligionists as direct relations—and to treat them with equal respect and seriousness even if they do not understand their exact relationships—to break out from the trap of thinking of the world from the perspective of the relatively small families we were raised in.

对我而言，构成我们每个人基因组的众多相互关联的人群，共同构建了一个相似的叙事，帮助我理解自身在世界中的位置，并避免被人类庞大的人口数量——数十亿——所吓倒。基因组革命在近几年揭示了混合在我们物种历史中的核心地位，这意味着我们彼此相连，并且在未来也将继续彼此相连。这种联系的叙事让我即使并非圣经中先祖的后裔，也能感受到犹太人的身份；即使我并非美洲原住民或最早的欧洲或非洲移民的后裔，也能感受到美国人的身份；即使我并非百年前祖先的后裔，也能感受到美国人的身份；即使我并非百年前祖先的后裔，也能感受到英语的语言；即使我并非来自我的直系祖先，也能感受到欧洲启蒙运动的思想传统。即便这些并非我的祖先所创造，即便我与他们并无密切的基因联系，我依然认同这些。我们各自的祖先并非重点。基因组革命为我们提供了一段共同的历史，如果我们认真对待这段历史，它应该能为我们提供一条替代种族主义和民族主义罪恶的途径，并让我们意识到我们都平等地享有人类遗产的权利。

For me, the multitude of interconnected populations that have contributed to each of our genomes provide a similar narrative that helps me to understand my own place in the world and to avoid being daunted by the vast number of people in our species—the immensity of the human population numbering in the billions. The centrality of mixture in the history of our species, as revealed in just the last few years by the genome revolution, means that we are all interconnected and that we will all keep connecting with one another in the future. This narrative of connection allows me to feel Jewish even if I may not be descended from the matriarchs and patriarchs of the Bible. I feel American, even if I am not descended from indigenous Americans or the first European or African settlers. I speak English, a language not spoken by my ancestors a hundred years ago. I come from an intellectual tradition, the European Enlightenment, which is not that of my direct ancestors. I claim these as my own, even if they were not invented by my ancestors, even if I have no close genetic relationship to them. Our particular ancestors are not the point. The genome revolution provides us with a shared history that, if we pay proper attention, should give us an alternative to the evils of racism and nationalism, and make us realize that we are all entitled equally to our human heritage.

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古代DNA的未来

The Future of Ancient DNA

考古学的第二次科学革命

The Second Scientific Revolution in Archaeology

考古学的第一次科学革命始于1949年，当时化学家威拉德·利比的一项发现彻底改变了这一领域，并为他赢得了11年后的诺贝尔奖。他证明，通过测量古代有机遗骸中携带14个核子（^而非更常见的12或13个核子）的碳原子的比例，可以确定碳首次进入食物链的时间。在地球上，放射性同位素碳-14主要由宇宙射线轰击大气层形成，使所有此类碳原子的比例维持在约万亿分之一的水平。在光合作用过程中，植物从大气中吸收碳并将其转化为糖。之后，碳被整合到所有其他生命分子中。生物体死亡后，一半的碳-14原子会在5730年内衰变为氮-14。这意味着古代遗骸中含有 14 个核子的碳原子所占的比例以已知的方式减少，这使得科学家能够确定碳进入生物体的时间，只要该日期小于大约 5 万年前（超过这个时间，碳-14 的比例太低，无法进行测量）。

The first scientific revolution in archaeology began in 1949, when the chemist Willard Libby made a discovery that would transform the field forever and win him the Nobel Prize eleven years later.¹ He showed that by measuring the fraction of carbon atoms in ancient organic remains that carry fourteen nucleons instead of the more common twelve or thirteen, he could determine the date when the carbon first entered the food chain. On earth, the radioactive isotope carbon-14 is mostly formed through the bombardment of the atmosphere by cosmic rays, maintaining the proportion of all carbon atoms of this type at a level of about one part per trillion. During photosynthesis, plants pull carbon out of the atmosphere and change it into sugar. From there, it gets integrated into all the other molecules of life. After a living thing dies, half the carbon-14 atoms decay into nitrogen-14 within 5,730 years. This means the fraction of all carbon atoms in ancient remains that have fourteen nucleons decreases in a known way, enabling scientists to determine a date for when the carbon entered a living thing as long as the date is less than about fifty thousand years ago (beyond that, the fraction of carbon-14 is too low to make a measurement).

放射性碳定年法彻底改变了考古学，使确定材料的真实年代成为可能，超越了以往的认知。通过研究遗骸的层理结构，考古学家们取得了意义深远的发现。在《文明之前：放射性碳革命与史前欧洲》一书中，^科林·伦弗鲁描述了放射性碳定年法如何揭示人类史前时期比之前认为的要早得多，并阐述了放射性碳革命如何推翻了欧洲史前时期所有重大创新都源自近东的假设。虽然农业和文字的确起源于近东，但金属加工和巨石阵等大型建筑的创新并非来自古埃及或古希腊。这些发现以及许多其他关于古代遗骸真实年代的发现，激发了人们对世界各地本土文化的全新认识。

Radiocarbon dating transformed archaeology, making it possible to determine the true age of materials, going beyond what was possible by studying the layering of remains. The discoveries that archaeologists made were profound. In Before Civilization: The Radiocarbon Revolution and Prehistoric Europe, Colin Renfrew described how radiocarbon dating showed that human prehistory extended much further back in time than had previously been thought, and described how the radiocarbon revolution overturned the assumption that all major innovations in European prehistory were imports from the Near East.² While farming and writing were indeed of Near Eastern origin, innovations in metalworking and monumental constructions such as the building of megaliths like those at Stonehenge were not derived from ancient Egypt or Greece. These findings and many other discoveries about the true age of ancient remains sparked a new appreciation for indigenous cultures everywhere.

放射性碳定年法已渗透到考古学的各个方面，这一点从一百多家为考古学家提供定年服务的放射性碳实验室以及严肃考古学家在研究生阶段学习的基本技能之一——如何批判性地解读放射性碳测年数据——都可见一斑。放射性碳定年法甚至改变了考古学家衡量时间的标准。古代中国人以皇帝登基为纪年；罗马人以他们城市的神话建城为纪年；犹太人则以《圣经》中记载的世界创世之日为纪年。如今，几乎所有人都以耶稣诞生的日期为基准来计算时间。而对于考古学家来说，时间现在以距今放射性碳衰变年数（BP）来衡量，BP的起始年份大约为1950年，即威拉德·利比发现放射性碳定年法的年份。

The penetration of radiocarbon dating into every aspect of archaeology is evident from the more than one hundred radiocarbon laboratories that provide dating to archaeologists as a service, and also from the fact that one of the basic skills serious archaeologists learn in graduate school is how to critically interpret radiocarbon dates. Radiocarbon dating has even changed archaeologists’ yardstick for time. The ancient Chinese measured years since emperors ascended the throne; the Romans since the mythical foundation of their city; and the Jews since the date of the creation of the world according to the Bible. Almost everyone today denominates years before or after the supposed birth date of Jesus. For archaeologists, time is now measured as the number of radiocarbon decay years Before Present (BP), defined as 1950, the approximate year when Willard Libby discovered radiocarbon dating.

放射性碳定年法的革命彻底改变了考古学这门学科。到了20世纪60年代，它不再仅仅是人文学科的一个分支，而是与自然科学建立了同样牢固的联系，并且对证据的要求也更高。3^在随后的时期，考古学家们采用了许多其他科学技术，包括利用浮选法来识别古代植物遗骸，以及研究除碳同位素以外的其他原子同位素的比例，以确定人类和动物的食物种类以及他们一生中是否迁徙过。考古学家们如今拥有了一套丰富的全新科学工具。他们所掌握的技术使他们能够以早期考古学家无法做到的方式分析他们挖掘的遗址，并得出更可靠的见解。

The radiocarbon revolution transformed the discipline of archaeology into one that by the 1960s was no longer only a branch of the humanities, and instead now had equally strong roots in the sciences, with a high standard of evidence now required to support claims.³ Many additional scientific techniques were adopted by archaeologists in the period that followed, including flotation to identify ancient plant remains, and study of ratios of atomic isotopes beyond those of carbon to determine the types of foods peoples and animals ate and whether they moved across the landscape in their lifetimes. The rich new suite of scientific tools that archaeologists now had at their disposal made it possible for them to analyze the sites they excavated in ways that had not been possible for earlier generations of archaeologists, and to arrive at insights that were more reliable.

人们很容易将古代DNA视为放射性碳定年法革命后考古学家可以使用的又一项新技术，但这低估了它的价值。在古代DNA出现之前，考古学家只能根据古代骨骼形状的变化和人们制造的器物类型来推测人口迁徙的迹象，但这些数据难以解读。然而，通过对古代人类的全基因组进行测序，现在我们可以极其详细地了解每个人之间的亲缘关系。

It is tempting to view ancient DNA as just one more new scientific technology that became available to archaeologists after the radiocarbon revolution, but that would be underestimating it. Prior to ancient DNA, archaeologists had hints of population movements based on the changes in the shapes of ancient skeletons and the types of artifacts people made, but these data were hard to interpret. But by sequencing whole genomes from ancient people, it is now possible to understand in exquisite detail how everyone is related.

衡量一项革命性技术的标准在于它揭示惊喜的速度，从这个意义上讲，古DNA比以往任何用于研究过去的科学技术都更具革命性，包括放射性碳定年法。一个更恰当的类比是十七世纪光学显微镜的发明，它使人们得以观察此前无人能想象的微生物和细胞世界。当一种新仪器开启通往未知世界的大门时，它所展现的一切都是全新的，一切都是惊喜。古DNA如今正经历着这样的过程。它为考古记录的变化究竟反映的是人口迁徙还是文化交流等问题提供了确凿的答案。它一次又一次地揭示出几乎无人预料的发现。

The measure of a revolutionary technology is the rate at which it reveals surprises, and in this sense, ancient DNA is more revolutionary than any previous scientific technology for studying the past, including radiocarbon dating. A more apt analogy is the seventeenth-century invention of the light microscope, which made it possible to visualize the world of microbes and cells that no one before had even imagined. When a new instrument opens up vistas onto a world that has not previously been explored, everything it shows is new, and everything is a surprise. This is what is happening now with ancient DNA. It is providing definitive answers to questions about whether changes in the archaeological record reflect movements of people or cultural communication. Again and again, it is revealing findings that almost no one expected.

人类古代DNA图谱

An Ancient DNA Atlas of Humanity

迄今为止，古DNA革命一直以欧洲为中心。截至2017年底，已发表的551个包含全基因组古DNA数据的样本中，近90%来自西欧亚大陆。这种对西欧亚大陆的关注反映了这样一个事实：大多数古DNA分析技术都起源于欧洲，而且欧洲的考古学家也长期以来一直在研究本土并收集遗骸。但古DNA革命正在扩展，并且已经取得了显著成果。关于西欧亚大陆以外人类历史的几项惊人发现，尤其值得一提的是美洲 ⁴ 和偏远太平洋岛屿 ⁵ 的人口迁徙。随着技术进步 ⁶使得从温暖甚至热带地区获取古代DNA成为可能，我毫不怀疑，在未来十年内，来自中亚、南亚、东亚和非洲的古代DNA也将揭示同样巨大的惊喜。这项研究的成果将是一部涵盖人类古DNA的图谱，其样本在时间和空间上都具有高度的密集性。我认为，就其对人类知识的贡献而言，这部图谱将堪比十五至十九世纪绘制的第一批世界地图。该图谱并不能解答关于人口历史的所有问题，但它将提供一个框架，一个基准，我们在研究新的考古遗址时将始终以此为依据。

So far, the ancient DNA revolution has been highly Eurocentric. Of 551 published samples with genome-wide ancient DNA data as of late 2017, almost 90 percent are from West Eurasia. The focus on West Eurasia is a reflection of the fact that it is in Europe that most of the technology for ancient DNA analysis was developed, and it is in Europe that archaeologists have been studying their own backyards and collecting remains for the longest period of time. But the ancient DNA revolution is spreading, and has already produced several startling discoveries about human history outside of West Eurasia, most notably about the peopling of the Americas⁴ and of the remote Pacific islands.⁵ As technical improvements⁶ have now made it possible to get ancient DNA from warm and even tropical places, I have no doubt that within the next decade, ancient DNA from central Asia, South Asia, East Asia, and Africa will reveal equally great surprises. The product of this effort will be an ancient DNA atlas of humanity, sampled densely through time and space. This will be a resource that I think will rival the first maps of the globe made between the fifteenth and nineteenth centuries in terms of its contribution to human knowledge. The atlas will not answer every question about population history, but it will provide a framework, a baseline to which we will always return when studying new archaeological sites.

随着这本图谱的构建，未来几年，我们完全有理由期待古代DNA领域会涌现出大量重大发现。古代DNA研究鲜有涉足的关键领域之一是四千年前至今的时期。迄今为止研究的大多数样本都来自更古老的时期，但我们当然可以从文字记载和考古证据中得知，近代——文字发展、复杂阶层社会和帝国兴起的时期——也经历了极其动荡的时期。即使在西欧亚大陆，古代DNA数据也如同仍在建设中的高速公路立交桥，悬停在半空中，尚未完全连接过去和现在的人群。利用DNA来探究这一时期发生的事情，无疑将丰富我们从其他学科获得的认知。

There is every reason to expect an avalanche of major discoveries from ancient DNA over the coming years as this atlas is built. One of the key frontiers that has hardly been touched by ancient DNA is the period between four thousand years ago and the present. The great majority of samples studied so far have been older, but of course we know from the written record as well as from archaeological evidence that more recent times—the period of the development of writing, complex stratified societies, and empires—have been extraordinarily eventful. The corpus of ancient DNA data even in West Eurasia is like a highway overpass still under construction and ending in midair, not quite connecting the populations of the past to those of the present. Using DNA to address what happened in this period will surely add to what we know from other disciplines.

为了连接过去四千年，将过去与现在联系起来，仅仅收集近期的古代DNA数据是不够的。那些在研究早期时期行之有效的统计方法，在分析近期数据时却失效了。特别是，基于四群体测试的方法之所以有效，是因为它们能够测量来自高度分化人群的祖先比例——这些截然不同的祖先就像示踪染料，其比例的变化可以被追踪。然而，在欧洲，迄今为止我们在古代DNA研究领域取得了最大的进展，我们知道，到四千年前，人类祖先的比例已经发生了显著变化。^几百年前，许多人群的祖先构成就与今天的人群高度相似。例如，在英国，我们知道，从四千五百年前开始，随着人们将死者与宽口钟形陶罐一同埋葬，古代英国人的祖先构成就与现代英国人非常相似。^然而，由此得出结论认为今天的英国人完全是“钟形陶罐文化人群”的后裔，那就错了。事实上，英国的人口结构已经受到多波来自欧洲大陆的移民的影响，这些移民的基因与钟形陶罐文化人群相似。我们需要新的、更灵敏的方法来确定英国人有多少祖先来自后来的移民潮。

To bridge the last four thousand years, to connect the past to the present, it is not sufficient to simply collect ancient DNA data from recent periods. The statistical methods that have worked so well for studying the earlier periods break down when examining data from more recent times. In particular, the methods based on Four Population Tests owe their power to measuring the proportions of ancestry from populations that are highly differentiated—the very different ancestries act like tracer dyes whose changing proportions can be tracked. However, in Europe, where we have made most progress in the ancient DNA revolution so far, we know that by four thousand years ago, many populations were already highly similar in their ancestry composition to those of today.⁷ For example, in Britain, we know that beginning after forty-five hundred years ago with people who buried their dead in association with wide-mouthed Bell Beaker pots, ancient Britons harbored a blend of ancestries very similar to that of present-day Britons.⁸ Yet it would be a mistake to conclude from this that the people of Britain today are descended without mixture from the “Beaker folk.” In fact, Britain’s population has been transformed by multiple subsequent waves of migration of continental people who were genetically similar to the people associated with Beaker burials. New, more sensitive methods are needed to determine how much ancestry in Britain derives from later waves.

为了应对这一挑战，统计遗传学家正在开发一类新的方法，使得追踪即使是祖先构成高度相似的人群的混合和迁徙成为可能。其秘诀在于关注被分析人群近期的共同历史，而非远古的共同历史。当同时分析足够多的样本时，就可以找到基因组中某些片段，这些片段使得个体对在过去大约四十代中拥有近亲祖先。通过聚焦这些基因组片段，我们可以了解人类历史上在这一时期（大约一千年）发生的事情。9^由于迄今为止古代DNA研究中可用的样本数量较少，这些方法尚未得到充分应用，因为只有极少数个体之间亲缘关系足够近，能够共享相同的长段DNA。但随着我们拥有古代DNA的个体数量的增加，我们可以分析以检测亲缘关系的个体对数量也会随着样本数量的平方而增加。按照目前古代DNA数据产生的速度，我们可以合理预期，在几年之内，像我所在的实验室这样的单个实验室每年就能获得数千个古代人类的全基因组数据。这将使我们能够详细记录人类群体在近几千年来的变迁。

To address this challenge, statistical geneticists are developing a new class of methods that make it possible to track mixtures and migrations even of populations that are highly similar in their deep ancestral composition. The secret is to focus on the recent shared history of the analyzed populations instead of the ancient shared history. When a sufficiently large number of samples are analyzed together, it is possible to find segments of the genome in which pairs of individuals share close ancestors over the last approximately forty generations, and by focusing on these segments of the genome, we can learn what happened in human history over this time frame (roughly one thousand years).⁹ With the small numbers of samples that have been available in ancient DNA studies so far, these methods have not been particularly useful because it is only the rare pair of individuals who are closely enough related to share identical long stretches of DNA. But as the number of individuals for whom we have ancient DNA increases, the number of pairs that we can analyze in order to detect relatedness increases according to the square of the number of samples. At the rate at which ancient DNA data are now being produced, it is reasonable to expect that within a few years, a single laboratory like mine will be producing genome-wide data from thousands of ancient people a year. This will make it possible to provide a detailed chronicle of how human populations have changed over recent millennia.

这种方法的优势已在2015年的《不列颠群岛居民》研究中得到体现，该研究抽样调查了超过研究人员选取了两千名英国当代居民，他们的祖父母均出生在彼此相距八十公里以内。 ¹⁰研究发现，按照传统方法衡量，英国人口的同质性很高。例如，衡量两个英国人群之间遗传分化的经典指标，比衡量欧洲人和东亚人之间遗传分化的指标小约一百倍。然而，尽管英国人口同质性很高，研究人员仍然能够通过寻找所有个体对都具有较高近期共同遗传祖先比例的群体，将英国人口划分为十七个界限分明的群体。他们将这些群体的位置绘制在地图上，观察到了非凡的遗传结构，这种结构在过去一千年里英国乡村地区人口不断迁徙的情况下依然存在，而人口迁徙本应使人口趋于同质化。这些群体的边界大致勾勒出了西南部的德文郡和康沃尔郡之间的界限；苏格兰北部海岸的奥克尼群岛；一个跨越爱尔兰海的、基本未分化的群体反映了近几个世纪以来苏格兰新教徒向北爱尔兰的迁徙；而在北爱尔兰境内，则存在两个截然不同且几乎不混合的群体，这无疑对应于因宗教信仰和英国统治下数百年的敌对关系而分裂的新教徒和天主教徒。这项仅针对现代人群进行的分析取得了成功，这为将该方法推广到更古老的样本带来了希望。在我的实验室里，我们已经生成了三百多位古代英国人的全基因组数据。通过将这些样本与包括“不列颠群岛居民”研究在内的现代英国人样本进行联合分析，我们期望能够在这个小小的世界角落里，将过去与现在联系起来。

The power of this approach can already be seen in the 2015 study “The People of the British Isles,” which sampled more than two thousand present-day individuals from the United Kingdom whose four grandparents were all born within eighty kilometers of one another.¹⁰ The study found that the British population was very homogeneous by conventional measures. For example, the classic measure of genetic differentiation between two British populations is about one hundred times smaller than the same measurement of population differentiation comparing Europeans to East Asians. Despite the homogeneity, however, the authors were able to cluster the British population into seventeen crisply defined groups by searching for groups in which all pairs of individuals have elevated rates of recently shared genetic ancestors. Plotting the positions onto a map, they observed extraordinary genetic structuring, which has persisted despite the fact that people have moved back and forth continually over the British countryside over the past millennium, a process that would have been expected to homogenize the population. The boundaries of the clusters mark out the border between the southwestern counties of Devon and Cornwall; the Orkney Islands off the north coast of Scotland; a largely undifferentiated cluster crossing the Irish Sea reflecting the migration of Scottish Protestants to Northern Ireland within the last few centuries; and within Northern Ireland, two distinctive and barely mixing clusters, which surely correspond to the Protestant and Catholic populations, divided by religion and hundreds of years of enmity under British rule. The success of this analysis, performed only on present-day people, gives hope for extending the approach to samples that are more ancient. In my laboratory, we already have generated genome-wide data on more than three hundred ancient Britons. Coanalyzing them with present-day Britons, including those from the “People of the British Isles” study, we expect to be able to connect the dots between the past and the present in this one small part of the world.

利用大量样本进行的古DNA研究也有望估算出过去不同时期的人口规模。对于文字发明之前的时期，我们几乎没有可靠的信息，但这对于理解人类历史和进化、经济和生态都至关重要。在一个拥有数亿人口的群体（例如汉族）中，一对……经过严格筛选的人群，由于其近四十代的祖先几乎完全不同，因此预计他们之间几乎没有或根本没有共同的DNA片段。相比之下，在人口较少的群体（例如人口不足百人的小安达曼岛原住民）中，所有个体之间都存在密切的亲缘关系，并且会通过许多共同的DNA片段来证明这种亲缘关系。通过测量人群的亲缘关系，已经能够正确地证明，过去几个世纪以来，英格兰的人口规模平均达到数百万。 ¹¹在目前正在进行的研究中，我和皮尔·帕拉马拉（Pier Palamara）已经证明，同样的方法也可以用来证明，大约八千年前安纳托利亚的早期农民的人口规模远大于同时期瑞典南部的狩猎采集者，这与农业能够支撑的人口密度更高的预期相符。我毫不怀疑，将这种方法应用于古代DNA研究，将为我们深入了解人口规模随时间推移的变化提供丰富的视角。

Ancient DNA studies with large numbers of samples also offer the promise of being able to estimate human population sizes at different times in the past, a topic about which we have almost no reliable information from the period earlier than the invention of writing, but which is important for understanding not just human history and evolution but also economics and ecology. In a population of many hundreds of millions (such as the Han Chinese), a pair of randomly chosen people is expected to have few if any shared segments of DNA within the last forty generations because they descend from almost entirely different ancestors over this period. By contrast, in a small population (like the indigenous people of Little Andaman Island, who have a census size of fewer than one hundred), all pairs of individuals are closely related and will show evidence of relatedness through many shared segments of DNA. Measuring how related people are has been used to show, correctly, that the size of the population of England in the last few centuries has averaged many millions.¹¹ In ongoing work, Pier Palamara and I have demonstrated that the same approach can be used to show that early farmers from Anatolia of around eight thousand years ago were part of much larger populations than the hunter-gatherers from southern Sweden who were their contemporaries, as expected based on the higher densities that can be supported by agriculture. I have no doubt that applying this approach to ancient DNA will provide rich insight into how populations changed in size over time.

古代DNA有望揭示人类生物学

Ancient DNA’s Promise for Revealing Human Biology

原则上，古DNA在揭示人类生物学随时间推移的演变方面，与在揭示人类迁徙和融合方面一样具有重要意义。然而，尽管古DNA在揭示人口变迁方面取得了巨大成功，但迄今为止，其对人类生物学的认识仍然有限。一个关键原因是，要追踪人类生物学随时间的变化，研究突变频率的变化至关重要。但这需要数百个样本，而迄今为止，古DNA的样本量相对较小，每个文化背景下仅有寥寥几个样本。如果我们获得了生活在农业转型后不久的一千名欧洲农民的全基因组数据，将会发生什么？将这些个体近期自然选择扫描的结果与对现代欧洲人进行的相同扫描结果进行比较，应该能够帮助我们了解人类适应的速度和性质在农业出现之前和之后是否发生了变化。自农业转型以来，自然选择的速度可能有所减缓。甚至有可能确定，由于医学进步，上个世纪自然选择的速度是否有所减缓。这些医学进步使得患有遗传疾病的个体能够生存并繁衍后代，而这些疾病原本会阻止他们生存和组建家庭。例如，视力不佳现在可以通过眼镜完全矫正；不孕不育现在可以通过医疗干预进行治疗；认知障碍现在可以通过药物和心理疗法进行控制。自然选择的这种变化可能导致突变的积累，从而改变种群中的这些性状。 ¹²

Ancient DNA in principle has just as much insight to offer about how human biology has changed over time as it does about human migrations and mixtures. And yet while the power of ancient DNA to reveal population transformations has been a runaway success, so far the insights into human biology have been limited. A key reason is that to track human biological change over time, it is important to be able to study how mutation frequencies change. But this requires hundreds of samples, and to date, the sample sizes of ancient DNA have been relatively small, just a handful from each cultural context. What will happen once we have genome-wide data from a thousand European farmers living shortly after the transition to agriculture? Comparing the results of a scan for recent natural selection in these individuals to the same scan performed in present-day Europeans should make it possible to understand whether the pace and nature of human adaptation has changed between preagricultural times and the time since the transition to agriculture. It might even be possible to determine whether natural selection has slowed down in the last century due to medical advances that allow individuals with genetic conditions that would have prevented them from surviving and having families to live and procreate. Examples of such medical conditions include poor eyesight, which can now be fully corrected with spectacles, or infertility, which can now be corrected by medical interventions, or cognitive challenges, which can now be controlled by medication and psychotherapy. It is possible that this change in natural selection is leading to a buildup of mutations contributing to altering these traits in the population.¹²

古DNA追踪生物学上重要突变频率变化速率的能力至关重要，这不仅因为它使我们能够追踪特定性状的演化，更重要的是，它提供了一种前所未有的工具，使我们能够理解自然选择的基本原理。人类进化生物学的一个核心问题是，人类进化通常是通过基因组中相对较少位点突变频率的大幅变化来实现的（例如色素沉着），还是通过大量突变频率的微小变化来实现的（例如身高）。 ¹³了解每种适应方式的相对重要性固然重要，但如果我们唯一可用的工具是分析生活在同一时期的人群，那么解决这个问题就变得更加困难。古DNA克服了这一障碍——即只能研究当下的局限。

The power of ancient DNA to track the rate at which the frequencies of biologically important mutations have changed is important not just because it offers the possibility of tracking the evolution of specific traits, but also because it provides a previously unavailable tool that we can use to understand the fundamental principles of how natural selection proceeds. A central question in human evolutionary biology is whether human evolution typically proceeds by large changes in mutation frequencies at relatively small numbers of positions in the genome, as in the case of pigmentation, or by small changes in frequencies at a very large number of mutations, as in the case of height.¹³ Understanding the relative importance of each type of adaptation is important, but addressing this question is made more challenging when the only tool available is analysis of people all of whom lived in a single window of time. Ancient DNA overcomes this obstacle—the time trap of only being able to study the present.

古代DNA研究也揭示了病原体的进化。在研磨人类遗骸时，我们有时会发现死者血液中微生物的DNA，这些微生物很可能是其死亡原因。这种方法证实，鼠疫耶尔森菌是公元14至17世纪黑死病 ¹⁴ 、公元6至8世纪罗马帝国查士丁尼瘟疫 ¹⁵以及大约5000年前欧亚草原地区埋葬的骨骼中至少7%死亡病例的病原体。 ¹⁶古代病原体研究还揭示了……古代麻风病的历史和起源 ¹⁷、肺结核 ¹⁸，以及植物方面的爱尔兰马铃薯饥荒 ¹⁹ 。如今，古代DNA研究正定期从寄生在我们体内的微生物（包括牙菌斑和粪便）中获取样本，从而提供有关我们祖先食物的信息 ²⁰ 。我们才刚刚开始挖掘这条新的信息宝库。

Ancient DNA research also reveals pathogen evolution. When grinding up human remains, we sometimes encounter DNA from microorganisms that were in an individual’s bloodstream when he or she died and so were the likely cause of death. This approach proved that the bacterium Yersinia pestis was the cause of the fourteenth-to-seventeenth-century CE Black Death,¹⁴ the sixth-to-eighth-century CE Justinianic plague of the Roman Empire,¹⁵ and an endemic plague that was responsible for at least about 7 percent of deaths in skeletons from burials across the Eurasian steppe after around five thousand years ago.¹⁶ Ancient pathogen studies have also revealed the history and origins of ancient leprosy,¹⁷ tuberculosis,¹⁸ and, in plants, the Irish potato famine.¹⁹ Ancient DNA studies are now regularly obtaining material from the microbes that inhabit us, including from dental plaque and feces, providing information about the food our ancestors ate.²⁰ We are only just beginning to mine this new seam of information.

驯服远古DNA革命的蛮荒西部

Taming the Wild West of the Ancient DNA Revolution

古DNA革命的发展速度令人振奋。这项技术日新月异，许多目前发表的论文所使用的方法，几年后就会过时。古DNA专家数量激增——例如，我所在的实验室已经培养了三位人才，他们各自创立了自己的古DNA实验室。一个主要趋势是专业化。古DNA的先驱们花费大量时间周游世界，前往偏远地区，与考古学家和当地官员交流，带回独特的遗骸，然后在他们的分子生物学实验室进行分析。前往异域探险，争相获取关键骨骼，是这种科研方式的核心。一些第二代古DNA研究人员沿用了这种模式。但包括我在内的其他人，则减少了出行，而是将大部分时间用于提升实验室技术或统计分析方面的专业知识，并通过与考古学家和人类学家日益平等的合作来获取研究样本。

The speed at which the ancient DNA revolution is moving is exhilarating. The technology is evolving so quickly that many papers being published right now use methods that will be obsolete within a few years. Ancient DNA specialists are multiplying—for example, my own laboratory has already graduated three people who have founded their own ancient DNA laboratories. A major trend is specialization. The pioneers of ancient DNA spent a large portion of their time traveling the world to remote locations, talking with archaeologists and local officials, and bringing back unique remains that they have then analyzed in their molecular biology laboratories. Travel to exotic places and a gold rush to obtain key bones are central to this way of doing science. Some in the second generation of ancient DNA research have adopted this model. But others, including myself, travel far less, and instead spend most of our time developing expertise in improved laboratory techniques or statistical analysis, obtaining the samples we study through increasingly equal partnerships with archaeologists and anthropologists.

古代DNA实验室也将变得更加专业化。目前，我们这些从事古代DNA研究的人有幸能够研究来自世界各地、不同历史时期的人群。我们就像罗伯特·胡克用显微镜观察他著作《显微图谱》中种类繁多的微小物体，又像十八世纪末的探险家航行到世界各地一样。然而，我们对任何研究课题的历史、考古和语言背景都只有浅显的了解，随着知识的增长，我们对这些背景的理解也会更加深入。要取得进展，就必须了解每个地区及其相关的具体问题。我预计，未来二十年，所有重要的人类学和考古学系，甚至历史学和生物学系，都会聘请古代DNA专家。这些专家将专注于特定区域的研究——例如东南亚或中国东北——他们的研究不会像我今天这样，在中国、美洲、欧洲和非洲之间来回切换。

Ancient DNA laboratories will also become more specialized. At present, we who are working on ancient DNA have the privilege of doing research on populations from all over the world and from a wide range of times. We are like Robert Hooke turning his microscope to describe an extraordinary array of tiny objects in his book Micrographia, or like explorers in the late eighteenth century, sailing to every corner of the globe. But we have at best a superficial knowledge of the historical and archaeological and linguistic background of any topic we work on, and as knowledge grows, a deeper understanding of each region and the specific questions associated with it will be needed to make progress. Over the next two decades, I expect that ancient DNA specialists will be hired into every serious department of anthropology and archaeology, even history and biology. The professionals hired into these roles will be specialized in studying particular areas—for example, Southeast Asia or northeastern China—and their research will not flit from China to America to Europe to Africa as mine does today.

古DNA检测也将走向专业化乃至职业化，建立起类似放射性碳定年法的服务实验室。古DNA服务实验室将对样本进行筛选，生成全基因组数据，并提供易于解读的报告，类似于目前商业个人祖源检测公司提供的报告。这些报告将确定物种、性别和亲缘关系，并揭示新研究的个体与先前已有数据记录的个体之间的关联。提交样本的研究人员将收到一份电子版数据，可随意使用。整个过程的成本不应超过放射性碳定年法的两倍。

Ancient DNA will also go the way of specialization and even professionalization when it comes to setting up service laboratories, analogous to the service laboratories that exist for radiocarbon dating. Ancient DNA service laboratories will screen samples, generate genome-wide data, and provide reports that are easily interpretable, much like those currently provided by commercial personal ancestry testing companies. The reports will determine species, sex, and family relationships, and reveal how newly studied individuals relate to individuals for whom there is previously reported data. The researchers submitting the samples will receive an electronic copy of the data to use in any way they wish. The whole process shouldn’t cost more than twice what radiocarbon dating does.

服务型实验室将会激增，但分析数据以研究人口历史的研究人员永远不会被完全取代。对利用DNA了解古代人口感兴趣的考古学家，如果希望利用这项技术解决任何较为微妙的问题，就始终需要与基因组学专家合作。从古代DNA中获取有关性别、物种、亲缘关系和祖先异常值的信息最终将成为常规操作。但是，利用古代DNA数据可以探究的更深层次的科学问题——例如人口如何混合和迁徙，以及自然选择如何随时间推移而发生——不太可能通过标准化的报告得到充分解答。

Service laboratories will proliferate, but researchers analyzing the data to study population history will never be entirely replaced. Archaeologists interested in learning about ancient populations using DNA will always need to partner with experts in genomics if they wish to use the technology to address any question that has subtlety. Getting information about sex, species, family relatedness, and ancestry outliers from ancient DNA will eventually be routine. But deeper scientific questions that can be accessed with ancient DNA data—such as how populations mixed and migrated, and how natural selection occurred over time—are unlikely ever to be addressed adequately through standardized reports.

我认为古代DNA实验室的未来发展方向，是基于放射性碳定年实验室中已经出现的一种模式。例如，牛津放射性碳加速器实验室收取费用处理大量样本，并利用这笔收入来支持一个工厂，该工厂能够以更低的成本、更高的效率和更高质量的质量批量生产常规年代数据。如果科学家们只局限于自身的研究问题，这一切或许并非可能。但他们却利用自己建立的放射性碳定年法工厂这一庞大的科研体系，开展前沿科学研究，例如托马斯·海厄姆（Thomas Higham）领导的研究，该研究澄清了尼安德特人在欧洲灭绝的记录，表明他们在与现代人类接触后的几千年内便在全球范围内消失。21^这也是我在麻省理工学院担任博士后研究员时所学到的模式。当时，我所在的六个测序中心之一负责为人类基因组计划进行大规模的测序工作，该计划由美国国立卫生研究院的大型数据生产合同资助。该中心的负责人，也就是我的导师埃里克·兰德（Eric Lander），也充分利用了测序中心的强大实力，致力于解决他感兴趣的科学问题。这也是我的模式：先建立一个强大的测序工厂，然后利用它来解答关于过去的深刻问题。

The future for ancient DNA laboratories that I find appealing is based on a model that has emerged among radiocarbon dating laboratories. For example, the Oxford Radiocarbon Accelerator Unit processes large numbers of samples for a fee, and uses this income stream to support a factory that churns out routine dates and produces data more cheaply, efficiently, and at higher quality than would be possible if its scientists limited themselves to their own questions. But its scientists then piggyback on the juggernaut of the radiocarbon dating factory they have built to do cutting-edge science, such as the study led by Thomas Higham that clarified the record on the demise of Neanderthals in Europe, showing that they disappeared everywhere within a few thousand years of contact with modern humans.²¹ This is also the model that I learned when I was a postdoctoral scientist at the Massachusetts Institute of Technology at one of the half dozen sequencing centers that carried out the brute-force work for the Human Genome Project, funded by large data production contracts from the U.S. National Institutes of Health. The center’s leader, my supervisor, Eric Lander, also took advantage of the fact that he could turn the power of his sequencing center to address scientific problems that intrigued him. This is my model too: to build a factory, and then to commandeer it to answer deep questions about the past.

出于对古代骸骨的尊重

Out of Respect for Ancient Bones

我七岁那年第一次去耶路撒冷，母亲带着哥哥和妹妹去了那里。那年夏天和接下来的一年，我们都住在祖父位于一个贫困的极端正统派犹太社区的公寓里。那里的男人们穿着黑色长袍，女人则穿着层层叠叠的保守连衣裙，戴着头巾。男孩们从早到晚都在宗教学校上课，但周五下午，也就是安息日之前，他们会提前放学，经常参加政治示威游行。在抗议活动中，他们有时会点燃垃圾箱，向警察投掷石块。我记得看到男孩们奔跑着，用布捂着脸，眼睛被警察发射的催泪瓦斯呛得直流泪。

I first went to Jerusalem when I was seven years old, taken there by my mother along with my older brother and younger sister. We stayed that summer and the next in an apartment that my grandfather owned in a poor, ultra-Orthodox neighborhood populated by men dressed in long black kaftans and women in layered modest dresses and headscarves. The boys attended morning-to-night religious schools, but on Friday afternoons before the Sabbath they were dismissed early and often joined political demonstrations. During the protests, they sometimes set fire to dumpsters and pelted policemen with stones. I remember watching the boys running, cloths pressed to faces, eyes streaming from the tear gas lobbed at them by the police.

这些抗议活动有些是为了回应大卫城的挖掘工作。大卫城位于耶路撒冷老城南侧的圣殿山山坡上，覆盖了大约三千年前成为犹太首都的大部分地区。抗议者们不满的是，挖掘工作可能会扰乱古代犹太人的墓葬，这在以色列的挖掘活动中始终存在着这种可能性。在抗议者看来，无论是意外还是出于科学研究的目的，打开墓葬都是一种亵渎行为。

Some of these protests were in response to excavations in the City of David, a site that spills down the hillside of the Temple Mount south of the Old City of Jerusalem, and covers much of the area that became the capital of Judaea after about three thousand years ago. The protesters were upset that the excavations would disturb ancient Jewish graves, an ever-present possibility when digging in Israel. For the protesters, the opening of graves, whether by accident or for scientific investigation, was desecration.

如果那些抗议者看到我的实验室现在每月都在处理数百具古代人的骨骼，他们会作何感想？或许他们并不太在意来自以色列以外的样本，但我认为这个问题更为普遍。我发现自己越来越倾向于思考是否应该打开坟墓，采集任何古代人类遗骸的样本。我们采集样本的许多人生前可能并不希望自己的遗骸被如此利用。

What would those protesters think of what my laboratory is doing now, grinding through the bones of hundreds of ancient people every month? Perhaps they would not care much about samples from outside Israel, but I think the issue is more general, and I have found myself reflecting more and more about opening up the graves and sampling the remains of any ancient human. It is likely that many of the people whose bones we sample would not have wanted their remains to be used in this way.

一些古代DNA专家和考古学家提出的一个论点是，我们研究的大多数骨骼都来自年代极其遥远的文化，与现代人群没有任何可追溯的联系。美国《美洲原住民墓葬保护与归还法案》中规定了这一法律标准，即当有证据表明遗骸与现代人群存在文化或生物学联系时，应将其归还给美洲原住民部落。然而，这一标准如今正在瓦解，例如距今约8500年的肯纳威克人骨骼和距今约10600年的灵洞骨骼，尽管与当今特定群体没有明确的文化或基因联系，却仍然被归还给了部落。^随着我们研究的骨骼年代越来越接近现代，思考现代对古代样本的主张所带来的影响至关重要。古代遗骸是真实存在的人的遗骸，我们或许只有在有充分理由的情况下才应该破坏其遗体的完整性。

One argument that some ancient DNA specialists and archaeologists have made is that most of the skeletons we are studying are from cultures so remote in time that they have no traceable connection to peoples of the present. This is the standard encoded in law in the U.S. Native American Graves Protection and Repatriation Act, which states that remains should be returned to Native American tribes when there is evidence of a cultural or biological connection to present-day peoples. However, this standard is now breaking down, as exemplified by the approximately 8,500-year-old Kennewick Man skeleton and the approximately 10,600-year-old Spirit Cave skeleton that are being returned to tribes despite having no clear cultural or genetic connections to specific groups living today.²² As we study skeletons that draw ever closer in time to the present, it is important to think about the implications of modern claims on ancient samples. Ancient remains are the remains of real people whose physical integrity we should perhaps only violate if we have good reasons.

2016年，我决定向一位拉比请教，这位拉比是我母亲的哥哥。他是一位正统派犹太教徒，这意味着他遵循犹太口传传统中详尽的教规。我希望他能乐于解答我的问题，因为他一直倡导在遵守正统教规的前提下，尽可能地让正统犹太教适应现代社会。这种包容性的理念被称为“开放正统派”。最近，他还创办了一所宗教学院，专门培养女性成为正统派拉比，而此前，该社区的女性很少担任这一职务。我被排除在外。我告诉他，在我的实验室里，我们正在研磨古代人的骨骼，其中许多人可能不希望他们的遗骸被打扰，我觉得我对此考虑得不够。他显然很困惑，并请我给他一些时间思考。之后，他回来给出了拉比在没有先例或先例可循时提供的指导意见。他说，所有人类的坟墓都是神圣不可侵犯的，但在某些特殊情况下，只要有可能促进理解、打破人与人之间的隔阂，就可以允许打开坟墓。

In 2016, I decided to ask a rabbi, in this case my mother’s brother, for counsel. He is Orthodox, which means that he follows the intricate rules specified in the Jewish Oral Tradition. I had a hope that he might be open to my question, as he has also been an advocate of adapting Orthodox Judaism as much as possible to the modern world while abiding by the constraints of its fixed rules, a movement of inclusivity that has been called “Open Orthodoxy”—most recently, he set up a religious seminary to train women as Orthodox rabbis, a role from which women in that community had previously been excluded. I told him that in my lab we were grinding through the bones of ancient peoples, many of whom might not have wanted their remains to be disturbed, and that I felt I had not thought enough about this. He was obviously troubled, and asked me for some time to think. Afterward he came back with the judgment a rabbi gives to provide guidance when there is no precedent set by earlier decisions or judgments made by other rabbis. He said all human graves are sacrosanct, but there are mitigating circumstances that make it permissible to open graves as long as there is potential to promote understanding, to break down barriers between people.

对人类变异的研究并非总是带来积极影响。在纳粹德国，如果20世纪30年代的科学技术允许，像我这样精通基因数据解读的人很可能会被委以重任，按祖先对人群进行分类。但在我们这个时代，古代DNA的研究成果几乎不容种族主义或民族主义的曲解。在这个领域，对真理本身的追求，其主要作用在于打破刻板印象、消除偏见，并揭示此前人们认为彼此无关的人群之间的联系。我乐观地认为，我和我的同事们的工作方向是促进理解，我珍惜我们有机会为那些我们有幸研究的古今人群尽心尽力的机会。我认为，我们的职责是引导古代DNA进入一个不仅属于遗传学家，也属于考古学家和公众的领域——充分发挥其揭示我们自身本质的非凡潜力。

The study of human variation has not always been a force for good. In Nazi Germany, someone with my expertise at interpreting genetic data would have been tasked with categorizing people by ancestry had that been possible with the science of the 1930s. But in our time, the findings from ancient DNA leave little solace for racist or nationalistic misinterpretation. In this field, the pursuit of truth for its own sake has overwhelmingly had the effect of exploding stereotypes, undercutting prejudice, and highlighting the connections among peoples not previously known to be related. I am optimistic that the direction of my work and that of my colleagues is to promote understanding, and I welcome our opportunity to do our best by the people, ancient and modern, whom we have been given the privilege to study. I see it as our role to midwife ancient DNA into a field that is not only the domain of geneticists, but also of archaeologists and the public—to realize its extraordinary potential to reveal who we are.

插图说明

Notes on the Illustrations

地图来源。所有地图均使用来自 Natural Earth ( http://www.naturalearthdata.com/ )的数据制作。

Map sources. All maps were made with data from Natural Earth (http://www.naturalearthdata.com/​).

图 1.面板 (a) 中的等高线基于 LL Cavalli-Sforza、P. Menozzi 和 A. Piazza 的论文“Demic Expansions and Human Evolution”的图 2A，发表于《科学》 259 (1993): 639–46。面板 (b) 中的等高线基于 W. Haak 等人的论文“Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe”的图 3 中的数字插值，发表于《自然》 522 (2015): 207–11。插值是使用 F. Jay 等人的 POPSutilities.R 软件进行的，参见“预测高山植物群体遗传结构对全球变暖的响应变化，分子生态学（2012）：2354–68”，以及 O. François 在“使用 R 运行类似结构群体遗传分析”中推荐的参数设置，2016 年 6 月，http://membres-timc.imag.fr/​Olivier.Francois/​tutoRstructure.pdf。

Figure 1. Contours in panel (a) are based on Fig. 2A of L. L. Cavalli-Sforza, P. Menozzi, and A. Piazza, “Demic Expansions and Human Evolution,” Science 259 (1993): 639–46. Contours in panel (b) are based on interpolation of the numbers shown in Fig. 3 of W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11. The interpolation was performed using the POPSutilities.R software of F. Jay et al., “Forecasting Changes in Population Genetic Structure of Alpine Plants in Response to Global Warming, Molecular Ecology (2012): 2354–68 and the parameter settings recommended in O. François, “Running Structure-like Population Genetic Analyses with R,” June 2016, http://membres-timc.imag.fr/​Olivier.Francois/​tutoRstructure.pdf.

图 2.该图显示了截至 2017 年 11 月 19 日作者内部实验室数据库中的 3,748 个独特个体，并按其出现年份进行了细分。

Figure 2. The plot shows the 3,748 unique individuals in the author’s internal laboratory database as of November 19, 2017, broken down by the year when they became available.

图 4.根据 Graham Coop 与作者分享的模拟结果，预计为当今个体贡献 DNA 的谱系祖先数量。模拟过程如 G. Coop，“我有多少遗传祖先？”，gcbias博客，2013 年 11 月 11 日，https://gcbias.org/​2013/​11/​11/​how-does-your-number-of-genetic-ancestors-grow-back-over-time/ 中所述。

Figure 4. The number of genealogical ancestors expected to have contributed DNA to a person living today is based on simulation results shared with the author by Graham Coop. The simulations were performed as described in G. Coop, “How Many Genetic Ancestors Do I Have,” gcbias blog, November 11, 2013, https://gcbias.org/​2013/​11/​11/​how-does-your-number-of-genetic-ancestors-grow-back-over-time/.

图 5.特定片段中，区分一个人从父亲那里继承的基因组和从母亲那里继承的基因组的突变数量，可以用来估计自基因组该位置的共同祖先以来经过的时间。图 (2) 基于 S. Mallick 等人在“西蒙斯基因组多样性”一文中报告的分析。“来自142个不同人群的300个基因组项目”（发表于《自然》杂志538卷（2016年）：201-206页）展示了250对非非洲基因组（实线）和44对撒哈拉以南非洲基因组在DNA等间距位置测得的最近共同祖先时间的平均值。图(3)展示了299对基因组中每个位置的最大估计时间，该数据基于同一研究的分析结果。

Figure 5. The number of mutations in a given segment that separate the genome a person receives from his or her father and the one he or she receives from his or her mother can be used to estimate how much time has elapsed since the common ancestor at that location in the genome. Panel (2), which is based on the analyses reported in S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6, shows the estimated times since the most recent shared ancestor averaged across 250 non-African genome pairs (solid line), and 44 sub-Saharan African genome pairs, measured at equally spaced locations in the DNA. Panel (3) shows the maximum estimated time at each location in the genome over 299 genome pairs and is based on analyses from the same study.

图 6.尼安德特人的大致分布范围改编自 J. Krause 等人的《中亚和西伯利亚的尼安德特人》，《自然》 449 (2007): 902–4 中的图 1。

Figure 6. The approximate range of the Neanderthals is adapted from Fig. 1 of J. Krause et al., “Neanderthals in Central Asia and Siberia,” Nature 449 (2007): 902–4.

图 7.共享突变的计数基于 RE Green 等人的补充在线材料表 S48 中的法国-圣尼安德特人比较，“尼安德特人基因组草图序列”，Science 328 (2010): 710–22。

Figure 7. The counts of shared mutations are based on the French-San-Neanderthal comparison in Table S48 of the Supplementary Online Materials of R. E. Green et al., “A Draft Sequence of the Neandertal Genome,” Science 328 (2010): 710–22.

图 8.该插图基于 Q. Fu 等人的论文“来自罗马尼亚的早期现代人类与近期尼安德特人祖先”中的图 2 数据，发表于《自然》 524 (2015): 216–19。

Figure 8. The illustration is based on the data in Fig. 2 of Q. Fu et al., “An Early Modern Human from Romania with a Recent Neanderthal Ancestor,” Nature 524 (2015): 216–19.

图 9.此图重新绘制了 Q. Fu 等人的论文“冰河时代欧洲的遗传历史”中的图 2 所示的数据，发表于《自然》 534 (2016): 200–5。

Figure 9. This illustration replots the data shown in Fig. 2. of Q. Fu et al., “The Genetic History of Ice Age Europe,” Nature 534 (2016): 200–5.

图 10。饼图数据来自 S. Mallick 等人发表于《自然》杂志538 (2016): 201–6 的文章“西蒙斯基因组多样性项目：来自 142 个不同种群的 300 个基因组”的补充表 2 中的 AJ 和 AK 列。每个种群均由该种群内个体的平均值表示。古老祖先的比例以数据集中任何种群中观察到的最大值的百分比表示。小于 0.03 的数值设为 0，大于 0.97 的数值设为 1。图中仅绘制了 47 个种群的子集，以突出显示地理覆盖范围并减少视觉混乱。

Figure 10. The pie chart data come from columns AJ and AK of Supplementary Table 2 of S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6. Each population is represented by an average of the individuals in that population. The proportion of archaic ancestry is expressed as a fraction of the maximum seen in any population in the dataset. Numbers less than 0.03 are set to 0 and numbers greater than 0.97 are set to 1. A subset of 47 populations is plotted to highlight the geographic coverage while reducing visual clutter.

图 13.此图描绘了 Q. Fu 等人在《自然》 534 (2016): 200–5 中描述的欧洲迁徙情况。冰盖范围是根据《不列颠百科全书在线》“欧洲冰盖范围”地图中的在线图表重新绘制的，网址为 https://www.britannica.com/​place/​Scandinavian-Ice-Sheet?oasmId=54573。

Figure 13. This illustration represents the migrations in Europe described in Q. Fu et al., “The Genetic History of Ice Age Europe,” Nature 534 (2016): 200–5. The ice extent is redrawn based on an online figure in “Extent of Ice Sheets in Europe,” Map. Encyclopaedia Britannica Online, https://www.britannica.com/​place/​Scandinavian-Ice-Sheet?oasmId=54573.

图 14。面板 (a) 根据 W. Haak 等人的论文“来自草原的大规模迁徙是欧洲印欧语系的来源”，发表于《自然》 522 (2015): 207–11，其中的扩展数据图 4 重新绘制。面板 (b) 及其插图经许可改编自 DW Anthony 和 D. Ringe 的论文“从语言学和考古学的角度看印欧语系的故乡”，发表于《语言学年鉴》 1 (2015): 199–219，其中的图 1 和图 2 。

Figure 14. Panel (a) is redrawn based on Extended Data Fig. 4 of W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11. Panel (b) and its inset are adapted with permission from Fig. 1 and Fig. 2 of D. W. Anthony and D. Ringe, “The Indo-European Homeland from Linguistic and Archaeological Perspectives,” Annual Review of Linguistics 1 (2015): 199–219.

图 15.所有三个面板中的散点图均基于 I. Lazaridis 等人的论文“米诺斯人和迈锡尼人的遗传起源”中的图 1b 所示的主成分分析，发表于《自然》 548 (2017): 214–8。x 轴和 y 轴经过旋转，大致与遗传和地理位置对齐。

Figure 15. The scatterplots in all three panels are based on the principal component analysis shown in Fig. 1b of I. Lazaridis et al., “Genetic Origins of the Minoans and Mycenaeans,” Nature 548 (2017): 214–8. The x- and y-axes are rotated to roughly align genetic and geographic positions.

图 16。饼图基于 180 位钟形杯文化个体的数据，这些个体拥有足够的古代 DNA 数据，可以对草原相关因素进行相对精确的估计。祖先。这些个体按当今欧洲的国家分组。数据来自 I. Olalde 等人的修订版，“烧杯现象和西北欧的基因组转型”，bioRxiv (2017): doi.org/​10.1101/​135962。

Figure 16. The pie charts are based on 180 Bell Beaker individuals for which there is enough ancient DNA data to make relatively precise estimates of steppe-related ancestry. The individuals are grouped by country within present-day Europe. The data are from a revised version of I. Olalde et al., “The Beaker Phenomenon and the Genomic Transformation of Northwest Europe,” bioRxiv (2017): doi.org/​10.1101/​135962.

图 17。 (a) 图中的南亚语系轮廓线是根据Joseph E. Schwartzberg 主编的《南亚历史地图集》 （牛津：牛津大学出版社，1992 年）中的图表重新绘制的。(b) 图中的散点图是基于 D. Reich 等人发表于《自然》杂志461 (2009): 489–94的文章“重建印度人口历史”中的图 3 的主成分分析结果绘制的。x轴和 y 轴经过旋转，以大致对齐遗传位置和地理位置。

Figure 17. In panel (a), the South Asian Language family contours are redrawn based on a plot in A Historical Atlas of South Asia, ed. Joseph E. Schwartzberg (Oxford: Oxford University Press, 1992). In panel (b), the scatterplot is based on the principal component analysis in Fig. 3 of D. Reich et al., “Reconstructing Indian Population History,” Nature 461 (2009): 489–94. The x- and y-axes are rotated to roughly align genetic and geographic positions.

图 18.小麦和大麦农业传播的地理轮廓和估计日期是根据 Dorian Fuller 提供的草图绘制的。地图西半部分的轮廓线遵循 F. Silva 和 M. Vander Linden 的图 2，“从 14C 推断的传播前沿振幅预测欧洲早期农民的遗传混合水平”，《科学报告》 7 (2017): 11985。

Figure 18. The geographic contours and estimated dates for the spread of wheat and barley agriculture are drawn based on a sketch kindly provided by Dorian Fuller. The contours for the western half of the map follow Fig. 2 of F. Silva and M. Vander Linden, “Amplitude of Travelling Front as Inferred From 14C Predicts Levels of Genetic Admixture Among European Early Farmers,” Scientific Reports 7 (2017): 11985.

图 19。北美冰盖和海岸线的位置数据来源于 AS Dyke 的《北美冰川消融概述，重点关注加拿大中部和北部》，载于Jürgen Ehlers 和 Philip L. Gibbard 主编的《第四纪冰川作用——范围和年代学，第二部分：北美》（阿姆斯特丹：Elsevier 出版社，2004 年），第 373-422 页（《第四纪冰川作用——范围和年代学》，第 380-383 页）。欧亚冰盖的位置数据来源于 H. Patton 等人的《欧亚冰盖复合体的冰川消融》，载于《第四纪科学评论》169 (2017)，第 148-172 页（《第四纪科学评论》），图 4。南美冰盖和海岸线的位置数据来源于 DJ Meltzer 的《第一批美洲人的起源、年代和迁徙》，载于《人类的过去》，第四版，图 5.1。克里斯·斯卡尔（伦敦：泰晤士和哈德逊出版社，预计 2018 年初出版），149-71 页。古代西伯利亚海岸线是插值得到的。

Figure 19. The North American ice sheet and shoreline positions are derived from the figures on pages 380–83 of A. S. Dyke, “An Outline of North American Deglaciation with Emphasis on Central and Northern Canada,” Quaternary Glaciations—Extent and Chronology, Part II: North America, ed. Jürgen Ehlers and Philip L. Gibbard (Amsterdam: Elsevier, 2004), 373–422. The Eurasian ice sheet positions are derived from Fig. 4 of H. Patton et al., “Deglaciation of the Eurasian Ice Sheet Complex,” Quaternary Science Reviews 169 (2017): 148–72. The South American ice and shoreline positions are derived form Fig. 5.1 of D. J. Meltzer, “The Origins, Antiquity and Dispersal of the First Americans,” in The Human Past, 4th Edition, ed. Chris Scarre (London: Thames and Hudson, expected early 2018), 149–71. The ancient Siberian shoreline is interpolated.

图 20。该图结合了 D. Reich 等人的“重建美洲原住民人口历史”一文中的图 2，发表于《自然》 488 (2012): 370–74，以及 P. Flegontov 等人的“北美古爱斯基摩人遗传遗产”一文中的图 5，发表于bioRxiv (2017): doi.org/​10.1101/​203018。

Figure 20. This illustration combines information from Fig. 2 of D. Reich et al., “Reconstructing Native American Population History,” Nature 488 (2012): 370–74 and Fig. 5 of P. Flegontov et al., “Paleo-Eskimo Genetic Legacy Across North America,” bioRxiv (2017): doi.org/​10.1101/​203018.

图 21.此图重新绘制了 P. Skoglund 等人的“美洲两个创始种群的遗传证据”一文中的图 1 的数据，发表于《自然》 525 (2015): 104–8。

Figure 21. This illustration replots the data from Fig. 1 of P. Skoglund et al., “Genetic Evidence for Two Founding Populations of the Americas,” Nature 525 (2015): 104–8.

图 23.根据 J. Diamond 和 P. Bellwood 的《农民及其语言：最初的扩张》， 《科学》 300 (2003): 597–603中的图 2，绘制了早期泰卡岱语、南亚语和南岛语使用者的可能迁徙路线。

Figure 23. The possible migration routes for early speakers of Tai-Kadai, Austroasiatic, and Austronesian languages are drawn based on Fig. 2 of J. Diamond and P. Bellwood, “Farmers and Their Languages: The First Expansions,” Science 300 (2003): 597–603.

图 24.图 (1) 中的古代海岸线近似于 A. Cooper 和 C. Stringer 的文章“丹尼索瓦人是否越过了华莱士线？” Science 342 (2013): 321–23 中的地图。

Figure 24. The ancient shoreline in panel (1) approximates the map in A. Cooper and C. Stringer, “Did the Denisovans Cross Wallace’s Line?” Science 342 (2013): 321–23.

图 25.此图基于 P. Skoglund 等人的“重建史前非洲人口结构”一文中的图 3D，发表于Cell 171 (2017): 59–71。

Figure 25. This illustration is based on Fig. 3D of P. Skoglund et al., “Reconstructing Prehistoric African Population Structure,” Cell 171 (2017): 59–71.

图 26.非洲语系轮廓与 MC Campbell、JB Hirbo、JP Townsend 和 SA Tishkoff 的《非洲大陆的人口迁徙和新世界的移民》，《遗传学和发育的最新观点》 29 (2014): 120–32 中图 3 所示的轮廓近似。与班图人扩张相关的可能迁徙路线与 Campbell 等人在《非洲大陆的人口》一书中描述的路线相似，但也采纳了 Scott MacEachern 的建议以及后续基因研究的发现，这些研究表明，向热带雨林以北的扩张可能并没有为当今东非的班图语使用者贡献多少祖先成分（GB Busby 等人，《撒哈拉以南非洲的混合》，eLi​​fe 5 (2016): e15266，以及 E. Patin 等人，《非洲和北美班图语人群的扩散和遗传适应》，Science 356 (2017): 543–46）。

Figure 26. The African language family contours approximate those shown in Fig. 3 of M. C. Campbell, J. B. Hirbo, J. P. Townsend, and S. A. Tishkoff, “The Peopling of the African Continent and the Diaspora into the New World,” Current Opinion in Genetics and Development 29 (2014): 120–32. Possible migratory routes associated with the Bantu expansion are similar to those in Campbell et al., “The Peopling of the African Continent,” but they also incorporate advice from Scott MacEachern and findings from subsequent genetic studies that suggest an expansion north of the tropical rainforest may not have contributed much of the ancestry of present-day Bantu speakers in East Africa (G. B. Busby et al., “Admixture into and Within Sub-Saharan Africa,” eLife 5 (2016): e15266, and E. Patin et al., “Dispersals and Genetic Adaptation of Bantu-Speaking Populations in Africa and North America,” Science 356 (2017): 543–46).

图 27。该图结合了 P. Skoglund 等人的“重建史前非洲人口结构”一文中的图 2B 和图 2C 中的数据，发表于Cell 171 (2017): 59–71。

Figure 27. This illustration combines numbers from Fig. 2B and Fig. 2C of P. Skoglund et al., “Reconstructing Prehistoric African Population Structure,” Cell 171 (2017): 59–71.

图 28.经 M. Karmin 等人许可改编自图 2，“Y 染色体多样性的近期瓶颈与全球文化变革相吻合”，《基因组研究》 25 (2015): 459–66。

Figure 28. Adapted with permission from Fig. 2 of M. Karmin et al., “A Recent Bottleneck of Y Chromosome Diversity Coincides with a Global Change in Culture,” Genome Research 25 (2015): 459–66.

笔记

Notes

介绍

Introduction

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1. Luigi Luca Cavalli-Sforza, Paolo Menozzi, and Alberto Piazza, The History and Geography of Human Genes (Princeton, NJ: Princeton University Press, 1994).

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10. R. E. Green et al., “A Draft Sequence of the Neandertal Genome,” Science 328 (2010): 710–22.

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13. W. Haak 等人，“来自草原的大规模迁徙是欧洲印欧语系的来源”，《自然》 522 (2015): 207–11。

13. W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11.

14. ME Allentoft 等人，“青铜时代欧亚大陆的人口基因组学”，《自然》 522 (2015): 167–72。

14. M. E. Allentoft et al., “Population Genomics of Bronze Age Eurasia,” Nature 522 (2015): 167–72.

15. I. Mathieson 等人，“230 个古代欧亚人的全基因组选择模式”，《自然》 528 (2015): 499–503。

15. I. Mathieson et al., “Genome-Wide Patterns of Selection in 230 Ancient Eurasians,” Nature 528 (2015): 499–503.

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18. Haak et al., “Massive Migration.”

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19. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24.

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20. P. Skoglund et al., “Genomic Insights into the Peopling of the Southwest Pacific,” Nature 538 (2016): 510–13.

21. Lazaridis 等人，“古代人类基因组”。

21. Lazaridis et al., “Ancient Human Genomes.”

22. Pickrell 和 Reich，“走向新历史”。

22. Pickrell and Reich, “Toward a New History.”

1 基因组如何解释我们是谁

1 How the Genome Explains Who We Are

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20. A. Kong 等人，“人类基因组的高分辨率重组图谱”，《自然遗传学》 31 (2002): 241–47。

20. A. Kong et al., “A High-Resolution Recombination Map of the Human Genome,” Nature Genetics 31 (2002): 241–47.

21. “伊丽莎白二世从威廉一世的血统”，Familypedia，http://familypedia.wikia.com/​wiki/​Descent_of_Elizabeth_II_from_William_I#Shorter_line_of_descent。

21. “Descent of Elizabeth II from William I,” Familypedia, http://familypedia.wikia.com/​wiki/​Descent_of_Elizabeth_II_from_William_I#Shorter_line_of_descent.

22. S. Mallick 等人，“西蒙斯基因组多样性计划：来自 142 个不同种群的 300 个基因组”，《自然》 538 (2016)：201-6。

22. S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6.

23. Green 等人，“草案序列”。

23. Green et al., “Draft Sequence.”

24. H. Li 和 R. Durbin，“从个体全基因组序列推断人类人口历史”，《自然》 475 (2011): 493–96。

24. H. Li and R. Durbin, “Inference of Human Population History from Individual Whole-Genome Sequences,” Nature 475 (2011): 493–96.

25. 同上。

25. Ibid.

26. S. Schiffels 和 R. Durbin，“从多个基因组序列推断人类人口规模和分离历史”，《自然遗传学》 46 (2014): 919–25。

26. S. Schiffels and R. Durbin, “Inferring Human Population Size and Separation History from Multiple Genome Sequences,” Nature Genetics 46 (2014): 919–25.

27. Mallick 等人，“西蒙斯基因组多样性计划”。

27. Mallick et al., “Simons Genome Diversity Project.”

28. I. Gronau 等人，“从个体基因组序列推断古代人类人口统计”，《自然遗传学》 43 (2011): 1031–34。

28. I. Gronau et al., “Bayesian Inference of Ancient Human Demography from Individual Genome Sequences,” Nature Genetics 43 (2011): 1031–34.

29. Mallick 等人，“西蒙斯基因组多样性计划”。

29. Mallick et al., “Simons Genome Diversity Project.”

30. PC Sabeti 等人，“从单倍型结构检测人类基因组中的近期正选择”，《自然》 419 (2002): 832–37；BF Voight、S. Kudaravalli、X. Wen 和 JK Pritchard，“人类基因组中近期正选择的图谱”，《PLoS 生物学》 4 (2006): e72。

30. P. C. Sabeti et al., “Detecting Recent Positive Selection in the Human Genome from Haplotype Structure,” Nature 419 (2002): 832–37; B. F. Voight, S. Kudaravalli, X. Wen, and J. K. Pritchard, “A Map of Recent Positive Selection in the Human Genome,” PLoS Biology 4 (2006): e72.

31. KM Teshima、G. Coop 和 M. Przeworski，“经验基因组扫描对选择性清除有多可靠？”，基因组研究16 (2006): 702–12。

31. K. M. Teshima, G. Coop, and M. Przeworski, “How Reliable Are Empirical Genomic Scans for Selective Sweeps?,” Genome Research 16 (2006): 702–12.

32. RD Hernandez 等人，“经典选择性清除在近期人类进化中很少见”，《科学》 331 (2011): 920–24。

32. R. D. Hernandez et al., “Classic Selective Sweeps Were Rare in Recent Human Evolution,” Science 331 (2011): 920–24.

33. SA Tishkoff 等人，“非洲和欧洲人类乳糖酶持久性的趋同适应”，《自然遗传学》 38 (2006): 31–40。

33. S. A. Tishkoff et al., “Convergent Adaptation of Human Lactase Persistence in Africa and Europe,” Nature Genetics 38 (2006): 31–40.

34. MC Turchin 等人，“欧洲身高相关 SNP 处站立变异的广泛选择证据”，《自然遗传学》 44 (2012): 1015–19。

34. M. C. Turchin et al., “Evidence of Widespread Selection on Standing Variation in Europe at Height-Associated SNPs,” Nature Genetics 44 (2012): 1015–19.

35. I. Mathieson 等人，“230 个古代欧亚人的全基因组选择模式”，《自然》 528 (2015): 499–503。

35. I. Mathieson et al., “Genome-Wide Patterns of Selection in 230 Ancient Eurasians,” Nature 528 (2015): 499–503.

36. Y. Field 等人，“过去 2000 年人类适应性的检测”，《科学》 354 (2016)：760–64。

36. Y. Field et al., “Detection of Human Adaptation During the Past 2000 Years,” Science 354 (2016): 760–64.

37. D. Welter 等人，“NHGRI GWAS 目录，SNP-性状关联的精选资源”，核酸研究42 (2014): D1001–6。

37. D. Welter et al., “The NHGRI GWAS Catalog, a Curated Resource of SNP-Trait Associations,” Nucleic Acids Research 42 (2014): D1001–6.

38. DB Goldstein，“常见遗传变异与人类特征”，《新英格兰医学杂志》 360（2009）：1696-98。

38. D. B. Goldstein, “Common Genetic Variation and Human Traits,” New England Journal of Medicine 360 (2009): 1696–98.

39. A. Okbay 等人，“全基因组关联研究鉴定出 74 个与教育程度相关的基因位点”，《自然》 533 (2016): 539–42；MT Lo 等人，“人格特质的全基因组分析鉴定出六个基因组位点，并显示与精神疾病的相关性”，《自然遗传学》 49 (2017): 152–56；G. Davies 等人，“英国生物银行 (N=112 151) 中认知功能和教育程度的全基因组关联研究”，《分子精神病学》 21 (2016): 758–67。

39. A. Okbay et al., “Genome-Wide Association Study Identifies 74 Loci Associated with Educational Attainment,” Nature 533 (2016): 539–42; M. T. Lo et al., “Genome-Wide Analyses for Personality Traits Identify Six Genomic Loci and Show Correlations with Psychiatric Disorders,” Nature Genetics 49 (2017): 152–56; G. Davies et al., “Genome-Wide Association Study of Cognitive Functions and Educational Attainment in UK Biobank (N=112 151),” Molecular Psychiatry 21 (2016): 758–67.

2 与尼安德特人的遭遇

2 Encounters with Neanderthals

1. 查尔斯·达尔文，《人类的由来及性选择》（伦敦：约翰·默里出版社，1871年）。

1. Charles Darwin, The Descent of Man, and Selection in Relation to Sex (London: John Murray, 1871).

2. Erik Trinkaus，《沙尼达尔尼安德特人》（纽约：学术出版社，1983 年）。

2. Erik Trinkaus, The Shanidar Neanderthals (New York: Academic Press, 1983).

3. D. Radovčić、AO Sršen、J. Radovčić 和 DW Frayer，“尼安德特人珠宝的证据：克拉皮纳改良的白尾鹰爪”，PLoS One 10 (2015)：e0119802。

3. D. Radovčić, A. O. Sršen, J. Radovčić, and D. W. Frayer, “Evidence for Neandertal Jewelry: Modified White-Tailed Eagle Claws at Krapina,” PLoS One 10 (2015): e0119802.

4. J. Jaubert 等人，“法国西南部布鲁尼凯尔洞穴深处的早期尼安德特人建筑”，《自然》 534 (2016): 111–14。

4. J. Jaubert et al., “Early Neanderthal Constructions Deep in Bruniquel Cave in Southwestern France,” Nature 534 (2016): 111–14.

5. WL Straus 和 AJE Cave，“尼安德特人的病理学和姿势”，《生物学季刊》 32 (1957): 348–63。

5. W. L. Straus and A. J. E. Cave, “Pathology and the Posture of Neanderthal Man,” Quarterly Review of Biology 32 (1957): 348–63.

6. 威廉·戈尔丁，《继承者》（伦敦：费伯出版社，1955 年）。

6. William Golding, The Inheritors (London: Faber and Faber, 1955).

7. Jean M. Auel，《洞熊家族》（纽约：皇冠出版社，1980 年）。

7. Jean M. Auel, The Clan of the Cave Bear (New York: Crown, 1980).

8. T. Higham 等人，“尼安德特人消失的时间和时空模式”，《自然》 512 (2014): 306–9。

8. T. Higham et al., “The Timing and Spatiotemporal Patterning of Neanderthal Disappearance,” Nature 512 (2014): 306–9.

9. T. Higham 等人，“雷恩洞穴（法国）的年代学及其对沙特尔佩龙文化中装饰品和人类遗骸背景的影响”，《美国国家科学院院刊》 107 (2010): 20234–39；O. Bar-Yosef 和 J.-G. Bordes，“谁是沙特尔佩龙文化的创造者？”，《人类进化杂志》 59 (2010): 586–93。

9. T. Higham et al., “Chronology of the Grotte du Renne (France) and Implications for the Context of Ornaments and Human Remains Within the Châtelperronian,” Proceedings of the National Academy of Sciences of the U.S.A. 107 (2010): 20234–39; O. Bar-Yosef and J.-G. Bordes, “Who Were the Makers of the Châtelperronian Culture?,” Journal of Human Evolution 59 (2010): 586–93.

10. R. Grün 等人，“与斯库尔人类墓葬相关的骨骼和牙齿的 U 系列和 ESR 分析”，《人类进化杂志》 49 (2005): 316–34。

10. R. Grün et al., “U-series and ESR Analyses of Bones and Teeth Relating to the Human Burials from Skhul,” Journal of Human Evolution 49 (2005): 316–34.

11. H. Valladas 等人，“以色列 Kebara 尼安德特人墓地的热释光测年”，《自然》 330 (1987): 159–60。

11. H. Valladas et al., “Thermo-Luminescence Dates for the Neanderthal Burial Site at Kebara in Israel,” Nature 330 (1987): 159–60.

12. E. Trinkaus 等人，“来自罗马尼亚 Peştera cu Oase 的早期现代人类”，美国国家科学院院刊100 (2003)：11231-36。

12. E. Trinkaus et al., “An Early Modern Human from the Peştera cu Oase, Romania,” Proceedings of the National Academy of Sciences of the U.S.A. 100 (2003): 11231–36.

13. M. Krings 等人，“尼安德特人 DNA 序列与现代人类的起源”，《细胞》 90 (1997): 19–30。

13. M. Krings et al., “Neandertal DNA Sequences and the Origin of Modern Humans,” Cell 90 (1997): 19–30.

14. C. Posth 等人，“深度分化的古老线粒体基因组为非洲基因流入尼安德特人提供了更低的时间界限”，《自然通讯》 8 (2017): 16046。

14. C. Posth et al., “Deeply Divergent Archaic Mitochondrial Genome Provides Lower Time Boundary for African Gene Flow into Neanderthals,” Nature Communications 8 (2017): 16046.

15. Krings 等人，“尼安德特人 DNA 序列”。

15. Krings et al., “Neandertal DNA Sequences.”

16. M. Currat 和 L. Excoffier，“现代人类在向欧洲扩张的过程中没有与尼安德特人混合”，PLoS Biology 2 (2004): e421；D. Serre 等人，“没有证据表明尼安德特人的线粒体 DNA 对早期现代人类有所贡献”，PLoS Biology 2 (2004): e57；M. Nordborg，“关于尼安德特人祖先的可能性”，American Journal of Human Genetics 63 (1998): 1237–40。

16. M. Currat and L. Excoffier, “Modern Humans Did Not Admix with Neanderthals During Their Range Expansion into Europe,” PLoS Biology 2 (2004): e421; D. Serre et al., “No Evidence of Neandertal mtDNA Contribution to Early Modern Humans,” PLoS Biology 2 (2004): e57; M. Nordborg, “On the Probability of Neanderthal Ancestry,” American Journal of Human Genetics 63 (1998): 1237–40.

17. RE Green 等人，“对一百万个尼安德特人 DNA 碱基对的分析”，《自然》 444 (2006): 330–36。

17. R. E. Green et al., “Analysis of One Million Base Pairs of Neanderthal DNA,” Nature 444 (2006): 330–36.

18. JD Wall 和 SK Kim，“尼安德特人基因组 DNA 序列的不一致性”，PLoS Genetics 3 (2007): 1862–66。

18. J. D. Wall and S. K. Kim, “Inconsistencies in Neanderthal Genomic DNA Sequences,” PLoS Genetics 3 (2007): 1862–66.

19. Krings 等人，“尼安德特人 DNA 序列”。

19. Krings et al., “Neandertal DNA Sequences.”

20. S. Sankararaman 等人，“尼安德特人和现代人类杂交的日期”，PLoS Genetics 8 (2012): e1002947。

20. S. Sankararaman et al., “The Date of Interbreeding Between Neandertals and Modern Humans,” PLoS Genetics 8 (2012): e1002947.

21. P. Moorjani 等人，“一种用于测定古代基因组年代的遗传方法提供了对过去 45,000 年人类世代间隔的直接估计”，美国国家科学院院刊113 (2016): 5652–7。

21. P. Moorjani et al., “A Genetic Method for Dating Ancient Genomes Provides a Direct Estimate of Human Generation Interval in the Last 45,000 Years,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 5652–7.

22. G. Coop，“关于：尼安德特人和现代人类杂交的日期”的思考，《霍尔丹的筛子》， 2012 年 9 月 18 日，https://haldanessieve.org/​2012/​09/​18/​thoughts-on-neandertal-article/。

22. G. Coop, “Thoughts On: The Date of Interbreeding Between Neandertals and Modern Humans,” Haldane’s Sieve, September 18, 2012, https://haldanessieve.org/​2012/​09/​18/​thoughts-on-neandertal-article/.

23. K. Prüfer 等人，“来自阿尔泰山脉的尼安德特人的完整基因组序列” ， 《自然》（2013 年）：doi：10.1038/nature 12886。

23. K. Prüfer et al., “The Complete Genome Sequence of a Neanderthal from the Altai Mountains,” Nature (2013): doi: 10.1038/nature 12886.

24. 同上。

24. Ibid.

25. 同上；M. Meyer 等人，“来自古丹尼索瓦人的高覆盖率基因组序列”，《科学》 338 (2012): 222–26；JD Wall 等人，“东亚人比欧洲人拥有更高水平的尼安德特人血统”，《遗传学》 194 (2013): 199–209。

25. Ibid; M. Meyer et al., “A High-Coverage Genome Sequence from an Archaic Denisovan Individual,” Science 338 (2012): 222–26; J. D. Wall et al., “Higher Levels of Neanderthal Ancestry in East Asians Than in Europeans,” Genetics 194 (2013): 199–209.

26. Q. Fu 等人，“冰河时代欧洲的遗传历史”，《自然》 534 (2016): 200–5。

26. Q. Fu et al., “The Genetic History of Ice Age Europe,” Nature 534 (2016): 200–5.

27. I. Lazaridis 等人，“从基因组学角度了解古代近东农业的起源”，《自然》 536 (2016): 419–24。

27. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24.

28. 特林考斯等人，“早期现代人类”。

28. Trinkaus et al., “An Early Modern Human.”

29. Q. Fu 等人，“来自罗马尼亚的早期现代人类与最近的尼安德特人祖先”，《自然》 524 (2015): 216–19。

29. Q. Fu et al., “An Early Modern Human from Romania with a Recent Neanderthal Ancestor,” Nature 524 (2015): 216–19.

30. N. Teyssandier、F. Bon 和 J.-G. Bordes，“在投射范围内：关于奥瑞纳文化在欧洲出现的一些思考”，《人类学研究杂志》 66 (2010): 209–29；P. Mellars，“考古学与现代人类在欧洲的扩散：解构‘奥瑞纳文化’”，《进化人类学》 15 (2006): 167–82。

30. N. Teyssandier, F. Bon, and J.-G. Bordes, “Within Projectile Range: Some Thoughts on the Appearance of the Aurignacian in Europe,” Journal of Anthropological Research 66 (2010): 209–29; P. Mellars, “Archeology and the Dispersal of Modern Humans in Europe: Deconstructing the ‘Aurignacian,’ ” Evolutionary Anthropology 15 (2006): 167–82.

31. M. Currat 和 L. Excoffier，“从观察到的基因渗入模式推断人类和尼安德特人之间存在强烈的生殖隔离”，美国国家科学院院刊108 (2011): 15129–34。

31. M. Currat and L. Excoffier, “Strong Reproductive Isolation Between Humans and Neanderthals Inferred from Observed Patterns of Introgression,” Proceedings of the National Academy of Sciences of the U.S.A. 108 (2011): 15129–34.

32. S. Sankararaman 等人，“现代人类尼安德特人祖先的基因组图谱”，《自然》 507 (2014): 354–57；B. Vernot 和 JMAkey，“从现代人类基因组中复活幸存的尼安德特人谱系”，《科学》 343（2014）：1017-21。

32. S. Sankararaman et al., “The Genomic Landscape of Neanderthal Ancestry in Present-Day Humans,” Nature 507 (2014): 354–57; B. Vernot and J. M. Akey, “Resurrecting Surviving Neandertal Lineages from Modern Human Genomes,” Science 343 (2014): 1017-21.

33. N. Patterson 等人，“人类和黑猩猩复杂物种形成的遗传证据”，《自然》 441 (2006): 1103–8。

33. N. Patterson et al., “Genetic Evidence for Complex Speciation of Humans and Chimpanzees,” Nature 441 (2006): 1103–8.

34. 同上；R. Burgess 和 Z. Yang，“在结合突变率变异和测序错误的贝叶斯溯祖模型下估计人科祖先种群大小”，分子生物学与进化25 (2008): 1975–94。

34. Ibid; R. Burgess and Z. Yang, “Estimation of Hominoid Ancestral Population Sizes Under Bayesian Coalescent Models Incorporating Mutation Rate Variation and Sequencing Errors,” Molecular Biology and Evolution 25 (2008): 1975–94.

35. JA Coyne 和 HA Orr，“物种形成的两条规则”，载于 Daniel Otte 和 John A. Endler 编辑的《物种形成及其后果》 （马萨诸塞州桑德兰：Sinauer Associates，1989 年），第 180-207 页。

35. J. A. Coyne and H. A. Orr, “Two Rules of Speciation,” in Speciation and Its Consequences, ed. Daniel Otte and John A. Endler (Sunderland, MA: Sinauer Associates, 1989), 180–207.

36. PK Tucker 等人，“两种小鼠杂交带中性染色体的突变渐变”，《进化》 46 (1992): 1146–63。

36. P. K. Tucker et al., “Abrupt Cline for Sex-Chromosomes in a Hybrid Zone Between Two Species of Mice,” Evolution 46 (1992): 1146–63.

37. H. Li 和 R. Durbin，“从个体全基因组序列推断人类人口历史”，《自然》 475 (2011): 493–96。

37. H. Li and R. Durbin, “Inference of Human Population History from Individual Whole-Genome Sequences,” Nature 475 (2011): 493–96.

38. T. Mailund 等人，“基于完整基因组的新的隔离与迁移模型推断出密切相关的类人猿物种之间存在非常不同的分化过程”，PLoS Genetics 8 (2012): e1003125。

38. T. Mailund et al., “A New Isolation with Migration Model Along Complete Genomes Infers Very Different Divergence Processes Among Closely Related Great Ape Species,” PLoS Genetics 8 (2012): e1003125.

39. JY Dutheil 等人，“人类-黑猩猩祖先 X 染色体上的强选择性清除解释了其低分化”，PLoS Genetics 11 (2015): e1005451。

39. J. Y. Dutheil et al., “Strong Selective Sweeps on the X Chromosome in the Human-Chimpanzee Ancestor Explain Its Low Divergence,” PLoS Genetics 11 (2015): e1005451.

40. Sankararaman 等人，“基因组景观”；B. Jégou 等人，“减数分裂基因在祖先减少的区域中富集”，分子生物学与进化34 (2017): 1974–80。

40. Sankararaman et al., “Genomic Landscape”; B. Jégou et al., “Meiotic Genes Are Enriched in Regions of Reduced Archaic Ancestry,” Molecular Biology and Evolution 34 (2017): 1974–80.

41. Q. Fu 等人，“冰河时代的欧洲”。

41. Q. Fu et al., “Ice Age Europe.”

42. I. Juric、S. Aeschbacher 和 G. Coop，“针对尼安德特人基因渗入的选择强度”，PLoS Genetics 12 (2016): e1006340；K. Harris 和 R. Nielsen，“尼安德特人基因渗入的遗传代价”，Genetics 203 (2016): 881–91。

42. I. Juric, S. Aeschbacher, and G. Coop, “The Strength of Selection Against Neanderthal Introgression,” PLoS Genetics 12 (2016): e1006340; K. Harris and R. Nielsen, “The Genetic Cost of Neanderthal Introgression,” Genetics 203 (2016): 881–91.

43. G. Bhatia 等人，“对 29,141 名非洲裔美国人进行全基因组扫描，未发现自混合以来有定向选择的证据”，《美国人类遗传学杂志》 95 (2014): 437–44。

43. G. Bhatia et al., “Genome-Wide Scan of 29,141 African Americans Finds No Evidence of Directional Selection Since Admixture,” American Journal of Human Genetics 95 (2014): 437–44.

44. 约翰·G·费希特 (Johann G. Fichte)，《Grundlage der gesamten Wissenschaftslehre》（德国耶拿：Gabler，1794 年）。

44. Johann G. Fichte, Grundlage der gesamten Wissenschaftslehre (Jena, Germany: Gabler, 1794).

3. 古代DNA打开了潘多拉魔盒

3 Ancient DNA Opens the Floodgates

1. J. Krause 等人，“中亚和西伯利亚的尼安德特人”，《自然》 449 (2007): 902–4。

1. J. Krause et al., “Neanderthals in Central Asia and Siberia,” Nature 449 (2007): 902–4.

2. J. Krause 等人，“来自西伯利亚南部未知人科动物的完整线粒体 DNA 基因组”，《自然》 464 (2010): 894-97。

2. J. Krause et al., “The Complete Mitochondrial DNA Genome of an Unknown Hominin from Southern Siberia,” Nature 464 (2010): 894-97.

3. C. Posth 等人，“深度分化的古老线粒体基因组为非洲基因流入尼安德特人提供了更低的时间界限”，《自然通讯》 8 (2017): 16046。

3. C. Posth et al., “Deeply Divergent Archaic Mitochondrial Genome Provides Lower Time Boundary for African Gene Flow into Neanderthals,” Nature Communications 8 (2017): 16046.

4. Krause 等人，“未知的人类”。

4. Krause et al., “Unknown Hominin.”

5. D. Reich 等人，“西伯利亚丹尼索瓦洞穴中一个古人类群体的遗传历史”，《自然》 468 (2010): 1053–60。

5. D. Reich et al., “Genetic History of an Archaic Hominin Group from Denisova Cave in Siberia,” Nature 468 (2010): 1053–60.

6. K. Prüfer 等人，“来自阿尔泰山脉的尼安德特人的完整基因组序列” ， 《自然》（2013 年）：doi：10.1038/nature 12886。

6. K. Prüfer et al., “The Complete Genome Sequence of a Neanderthal from the Altai Mountains,” Nature (2013): doi: 10.1038/nature 12886.

7. Jerry A. Coyne 和 H. Allen Orr，《物种形成》（马萨诸塞州桑德兰：Sinauer Associates，2004 年）。

7. Jerry A. Coyne and H. Allen Orr, Speciation (Sunderland, MA: Sinauer Associates, 2004).

8. S. Sankararaman、S. Mallick、N. Patterson 和 D. Reich，“现代人类中丹尼索瓦人和尼安德特人祖先的综合图景”，《当代生物学》 26 (2016): 1241–47。

8. S. Sankararaman, S. Mallick, N. Patterson, and D. Reich, “The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans,” Current Biology 26 (2016): 1241–47.

9. P. Moorjani 等人，“一种用于测定古代基因组年代的遗传方法提供了对过去 45,000 年人类世代间隔的直接估计”，美国国家科学院院刊113 (2016): 5652–7。

9. P. Moorjani et al., “A Genetic Method for Dating Ancient Genomes Provides a Direct Estimate of Human Generation Interval in the Last 45,000 Years,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 5652–7.

10. Sankararaman 等人，“综合景观”。

10. Sankararaman et al., “Combined Landscape.”

11. D. Reich 等人，“丹尼索瓦人种混合与现代人类首次向东南亚和大洋洲的扩散”，《美国人类遗传学杂志》 89 (2011): 516–28。

11. D. Reich et al., “Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania,” American Journal of Human Genetics 89 (2011): 516–28.

12. Q. Fu 等人，“中国天元洞早期现代人类的 DNA 分析”，美国国家科学院院刊110 (2013): 2223–27；M. Yang 等人，“来自亚洲的 40,000 年前个体为了解欧亚大陆早期人口结构提供了见解”，当代生物学27 (2017): 3202–8。

12. Q. Fu et al., “DNA Analysis of an Early Modern Human from Tianyuan Cave, China,” Proceedings of the National Academy of Sciences of the U.S.A. 110 (2013): 2223–27; M. Yang et al., “40,000-Year-Old Individual from Asia Provides Insight into Early Population Structure in Eurasia,” Current Biology 27 (2017): 3202–8.

13. Prüfer 等人，“完整基因组”。

13. Prüfer et al., “Complete Genome.”

14. CB Stringer 和 I. Barnes，“解读丹尼索瓦人”，美国国家科学院院刊112 (2015): 15542–43。

14. C. B. Stringer and I. Barnes, “Deciphering the Denisovans,” Proceedings of the National Academy of Sciences of the U.S.A. 112 (2015): 15542–43.

15. GA Wagner 等人，“德国毛尔人海德堡模式遗址的放射性测年”，美国国家科学院院刊107 (2010): 19726–30。

15. G. A. Wagner et al., “Radiometric Dating of the Type-Site for Homo Heidelbergensis at Mauer, Germany,” Proceedings of the National Academy of Sciences of the U.S.A. 107 (2010): 19726–30.

16. C. Stringer，“海德堡人（Schoetensack 1908）的地位”，进化人类学21 (2012): 101–7。

16. C. Stringer, “The Status of Homo heidelbergensis (Schoetensack 1908),” Evolutionary Anthropology 21 (2012): 101–7.

17. A. Brumm 等人，“弗洛勒斯岛已知最古老的人类化石的年龄和背景”，《自然》 534 (2016): 249–53。

17. A. Brumm et al., “Age and Context of the Oldest Known Hominin Fossils from Flores,” Nature 534 (2016): 249–53.

18. Reich 等人，“Denisova 混合物”。

18. Reich et al., “Denisova Admixture.”

19. Prüfer 等人，“完整基因组”。

19. Prüfer et al., “Complete Genome.”

20. 同上；Sankararaman 等人，“综合景观”。

20. Ibid.; Sankararaman et al., “Combined Landscape.”

21. E. Huerta-Sánchez 等人，“藏族人因丹尼索瓦人样 DNA 渗入而产生的海拔适应性”，《自然》 512 (2014): 194–97。

21. E. Huerta-Sánchez et al., “Altitude Adaptation in Tibetans Caused by Introgression of Denisovan-like DNA,” Nature 512 (2014): 194–97.

22. FH Chen 等人，“农业促进了人类在公元前 3600 年后在青藏高原的永久居住”，《科学》 347 (2015): 248–50。

22. F. H. Chen et al., “Agriculture Facilitated Permanent Human Occupation of the Tibetan Plateau After 3600 B.P.,” Science 347 (2015): 248–50.

23. S. Sankararaman 等人，“现代人类尼安德特人祖先的基因组图景”，《自然》 507 (2014): 354–57；B. Vernot 和 JM Akey，“从现代人类基因组中复活幸存的尼安德特人谱系”， 《科学》 343 (2014): 1017–21。

23. S. Sankararaman et al., “The Genomic Landscape of Neanderthal Ancestry in Present-Day Humans,” Nature 507 (2014): 354–57; B. Vernot and J. M. Akey, “Resurrecting Surviving Neandertal Lineages from Modern Human Genomes,” Science 343 (2014): 1017–21.

24. Prüfer 等人，“完整基因组”。

24. Prüfer et al., “Complete Genome.”

25. GP Rightmire，“直立人和中更新世人族：脑容量、头骨形状和物种识别”，《人类进化杂志》 65（2013）：223-52。

25. G. P. Rightmire, “Homo erectus and Middle Pleistocene Hominins: Brain Size, Skull Form, and Species Recognition,” Journal of Human Evolution 65 (2013): 223–52.

26. M. Martinón-Torres 等人，“更新世时期人类扩散的牙齿证据”，《美国国家科学院院刊》 104 (2007): 13279–82；M. Martinón-Torres、R. Dennell 和 JMB de Castro，“丹尼索瓦人并非‘走出非洲’的故事”，《期刊》人类进化60 (2011): 251–55；JMB de Castro 和 M. Martinón-Torres，“欧洲更新世人类人口演化的新模型”，第四纪国际295 (2013): 102–12。

26. M. Martinón-Torres et al., “Dental Evidence on the Hominin Dispersals During the Pleistocene,” Proceedings of the National Academy of Sciences of the U.S.A. 104 (2007): 13279–82; M. Martinón-Torres, R. Dennell, and J. M. B. de Castro, “The Denisova Hominin Need Not Be an Out of Africa Story,” Journal of Human Evolution 60 (2011): 251–55; J. M. B. de Castro and M. Martinón-Torres, “A New Model for the Evolution of the Human Pleistocene Populations of Europe,” Quaternary International 295 (2013): 102–12.

27. 德卡斯特罗和马蒂农-托雷斯，“新模式”。

27. De Castro and Martinón-Torres, “A New Model.”

28. JL Arsuaga 等人，“尼安德特人的根源：来自 Sima de los Huesos 的颅骨和年代学证据”，Science 344 (2014)：1358–63； M. Meyer 等人，“来自 Sima de los Huesos 的古人类的线粒体基因组序列”，Nature 505 (2014)：403-6。

28. J. L. Arsuaga et al., “Neandertal Roots: Cranial and Chronological Evidence from Sima de los Huesos,” Science 344 (2014): 1358–63; M. Meyer et al., “A Mitochondrial Genome Sequence of a Hominin from Sima de los Huesos,” Nature 505 (2014): 403–6.

29. M. Meyer 等人，“来自中更新世西玛德洛斯韦索斯人种的核 DNA 序列”，《自然》 531 (2016): 504–7。

29. M. Meyer et al., “Nuclear DNA Sequences from the Middle Pleistocene Sima de los Huesos Hominins,” Nature 531 (2016): 504–7.

30. Meyer 等人，“线粒体基因组”；Meyer 等人，“核 DNA 序列”。

30. Meyer et al., “A Mitochondrial Genome”; Meyer et al., “Nuclear DNA Sequences.”

31. Krause 等人，“未知的人类”；Reich 等人，“遗传史”。

31. Krause et al., “Unknown Hominin”; Reich et al., “Genetic History.”

32. Posth 等人，“深度分化的古风”。

32. Posth et al., “Deeply Divergent Archaic.”

33. 同上。

33. Ibid.

34. Prüfer 等人，“完整基因组”。

34. Prüfer et al., “Complete Genome.”

35. S. McBrearty 和 AS Brooks，“未发生的革命：对现代人类行为起源的新解释”，《人类进化杂志》 39 (2000): 453–563。

35. S. McBrearty and A. S. Brooks, “The Revolution That Wasn’t: A New Interpretation of the Origin of Modern Human Behavior,” Journal of Human Evolution 39 (2000): 453–563.

36. M. Kuhlwilm 等人，“早期现代人类向东部尼安德特人的古代基因流动”，《自然》 530 (2016): 429–33。

36. M. Kuhlwilm et al., “Ancient Gene Flow from Early Modern Humans into Eastern Neanderthals,” Nature 530 (2016): 429–33.

4 人类的幽灵

4 Humanity’s Ghosts

1. 查尔斯·R·达尔文，《物种起源》，通过自然选择或在生存斗争中保存优势种族（伦敦：约翰·默里出版社，1859 年）。

1. Charles R. Darwin, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life (London: John Murray, 1859).

2. C. Becquet 等人，“黑猩猩种群的遗传结构”，PLoS Genetics 3 (2007): e66。

2. C. Becquet et al., “Genetic Structure of Chimpanzee Populations,” PLoS Genetics 3 (2007): e66.

3. RE Green 等人，“尼安德特人基因组草图序列”，《科学》 328 (2010): 710–22。

3. R. E. Green et al., “A Draft Sequence of the Neandertal Genome,” Science 328 (2010): 710–22.

4. NJ Patterson 等人，“人类历史上的古代混合”，遗传学192 (2012): 1065–93。

4. N. J. Patterson et al., “Ancient Admixture in Human History,” Genetics 192 (2012): 1065–93.

5. 恩斯特·迈尔，《从动物学家的角度看系统学和物种起源》（纽约：哥伦比亚大学出版社，1942 年）。

5. Ernst Mayr, Systematics and the Origin of Species from the Viewpoint of a Zoologist (New York: Columbia University Press, 1942).

6. JK Pickrell 和 D. Reich，“基于古代 DNA 的人类基因新历史和地理”，遗传学趋势30 (2014): 377–89。

6. J. K. Pickrell and D. Reich, “Toward a New History and Geography of Human Genes Informed by Ancient DNA,” Trends in Genetics 30 (2014): 377–89.

7. AR Templeton，“人类的生物种族”，生物和生物医学科学史与哲学研究44 (2013): 262–71。

7. A. R. Templeton, “Biological Races in Humans,” Studies in History and Philosophy of Biological and Biomedical Science 44 (2013): 262–71.

8. M. Raghavan 等人，“西伯利亚旧石器时代晚期基因组揭示了美洲原住民的双重祖先”，《自然》 505 (2014): 87–91。

8. M. Raghavan et al., “Upper Palaeolithic Siberian Genome Reveals Dual Ancestry of Native Americans,” Nature 505 (2014): 87–91.

9. I. Lazaridis 等人，“古代人类基因组表明现代欧洲人有三个祖先群体”，《自然》 513 (2014): 409–13。

9. I. Lazaridis et al., “Ancient Human Genomes Suggest Three Ancestral Populations for Present-Day Europeans,” Nature 513 (2014): 409–13.

10. I. Lazaridis 等人，“从基因组学角度了解古代近东农业的起源”，《自然》 536 (2016): 419–24。

10. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24.

11. 同上。

11. Ibid.

12. F. Broushaki 等人，“来自东部肥沃新月地带的早期新石器时代基因组”cent”，《科学》 353（2016）：499-503；ER Jones 等人，“旧石器时代晚期基因组揭示了现代欧亚人的深厚根源”，《自然通讯》 6（2015）：8912。

12. F. Broushaki et al., “Early Neolithic Genomes from the Eastern Fertile Crescent,” Science 353 (2016): 499–503; E. R. Jones et al., “Upper Palaeolithic Genomes Reveal Deep Roots of Modern Eurasians,” Nature Communications 6 (2015): 8912.

13. BM Henn 等人，“北非人的基因组祖先支持回归非洲的迁徙”，PLoS Genetics 8 (2012): e1002397。

13. B. M. Henn et al., “Genomic Ancestry of North Africans Supports Back-to-Africa Migrations,” PLoS Genetics 8 (2012): e1002397.

14. Lazaridis 等人，“基因组学见解”。

14. Lazaridis et al., “Genomic Insights.”

15. O. Bar-Yosef，“非洲与西南亚之间的更新世联系：考古学视角”，《非洲考古评论》5（1987）：29-38。

15. O. Bar-Yosef, “Pleistocene Connections Between Africa and Southwest Asia: An Archaeological Perspective,” African Archaeological Review 5 (1987): 29–38.

16. Lazaridis 等人，“基因组学见解”。

16. Lazaridis et al., “Genomic Insights.”

17. Lazaridis 等人，“古代人类基因组”。

17. Lazaridis et al., “Ancient Human Genomes.”

18. Q. Fu 等人，“冰河时代欧洲的遗传历史”，《自然》 534 (2016): 200–5。

18. Q. Fu et al., “The Genetic History of Ice Age Europe,” Nature 534 (2016): 200–5.

19. Q. Fu 等人，“来自西伯利亚西部的 45,000 年前现代人类的基因组序列”，《自然》 514 (2014): 445–49。

19. Q. Fu et al., “Genome Sequence of a 45,000-Year-Old Modern Human from Western Siberia,” Nature 514 (2014): 445–49.

20. Q. Fu 等人，“来自罗马尼亚的早期现代人类与最近的尼安德特人祖先”，《自然》 524 (2015): 216–19。

20. Q. Fu et al., “An Early Modern Human from Romania with a Recent Neanderthal Ancestor,” Nature 524 (2015): 216–19.

21. FG Fedele、B. Giaccio 和 I. Hajdas，“从坎帕尼亚火山碎屑流喷发看 40,000 年前的时间尺度和文化过程，西欧亚大陆”，《人类进化杂志》 55 (2008): 834–57；A. Costa 等人，“量化坎帕尼亚火山碎屑流超级喷发的火山灰扩散和影响”，《地球物理研究快报》 39 (2012): L10310。

21. F. G. Fedele, B. Giaccio, and I. Hajdas, “Timescales and Cultural Process at 40,000 BP in the Light of the Campanian Ignimbrite Eruption, Western Eurasia,” Journal of Human Evolution 55 (2008): 834–57; A. Costa et al., “Quantifying Volcanic Ash Dispersal and Impact of the Campanian Ignimbrite Super-Eruption,” Geophysical Research Letters 39 (2012): L10310.

22. Fedele 等人，“时间尺度和文化过程”。

22. Fedele et al., “Timescales and Cultural Process.”

23. A. Seguin-Orlando 等人，“欧洲人的基因组结构可追溯到至少 36,200 年前”，《科学》 346 (2014): 1113–18。

23. A. Seguin-Orlando et al., “Genomic Structure in Europeans Dating Back at Least 36,200 Years,” Science 346 (2014): 1113–18.

24. Fu等人，“冰河时代的欧洲”。

24. Fu et al., “Ice Age Europe.”

25. Andreas Maier，《中欧马格德林文化：区域多样性和内部变异性》（荷兰多德雷赫特：施普林格出版社，2015 年）。

25. Andreas Maier, The Central European Magdalenian: Regional Diversity and Internal Variability (Dordrecht, The Netherlands: Springer, 2015).

26. Fu等人，“冰河时代的欧洲”。

26. Fu et al., “Ice Age Europe.”

27. NA Rosenberg 等人，“渐变群、聚类以及研究设计对人类群体结构推断的影响”，PLoS Genetics 1 (2005): e70；G. Coop 等人，“地理在人类适应中的作用”，PLoS Genetics 5 (2009): e1000500。

27. N. A. Rosenberg et al., “Clines, Clusters, and the Effect of Study Design on the Inference of Human Population Structure,” PLoS Genetics 1 (2005): e70; G. Coop et al., “The Role of Geography in Human Adaptation,” PLoS Genetics 5 (2009): e1000500.

28. Q. Fu 等人，“中国天元洞早期现代人类的 DNA 分析”，美国国家科学院院刊110 (2013): 2223–27。

28. Q. Fu et al., “DNA Analysis of an Early Modern Human from Tianyuan Cave, China,” Proceedings of the National Academy of Sciences of the U.S.A. 110 (2013): 2223–27.

29. Fu 等人，“近期尼安德特人祖先”；W. Haak 等人，“来自草原的大规模迁徙是欧洲印欧语系的来源”，《自然》 522 (2015): 207–11。

29. Fu et al., “Recent Neanderthal Ancestor”; W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11.

30. R. Pinhasi 等人，“从人类岩骨内耳部分获得最佳古代 DNA 产量”，PLoS One 10 (2015): e0129102。

30. R. Pinhasi et al., “Optimal Ancient DNA Yields from the Inner Ear Part of the Human Petrous Bone,” PLoS One 10 (2015): e0129102.

31. Lazaridis 等人，“基因组学见解”。

31. Lazaridis et al., “Genomic Insights.”

32. 同上；Broushaki 等人，“早期新石器时代基因组”。

32. Ibid.; Broushaki et al., “Early Neolithic Genomes.”

33. I. Olalde 等人，“7000 年前欧洲中石器时代衍生的免疫和祖先色素沉着等位基因”，《自然》 507 (2014): 225–28。

33. I. Olalde et al., “Derived Immune and Ancestral Pigmentation Alleles in a 7,000-Year-Old Mesolithic European,” Nature 507 (2014): 225–28.

34. I. Mathieson 等人，“230 个古代欧亚人的全基因组选择模式”，《自然》 528 (2015): 499–503。

34. I. Mathieson et al., “Genome-Wide Patterns of Selection in 230 Ancient Eurasians,” Nature 528 (2015): 499–503.

35. I. Mathieson 等人，“东南欧的基因组历史”，bioRxiv (2017): doi.org/​10.1101/​135616。

35. I. Mathieson et al., “The Genomic History of Southeastern Europe,” bioRxiv (2017): doi.org/​10.1101/​135616.

36. Haak 等人，“大规模迁徙”；ME Allentoft 等人，“青铜时代欧亚大陆的人口基因组学”，《自然》 522 (2015): 167–72。

36. Haak et al., “Massive Migration”; M. E. Allentoft et al., “Population Genomics of Bronze Age Eurasia,” Nature 522 (2015): 167–72.

37. 坦普尔顿，《生物种族》。

37. Templeton, “Biological Races.”

5 现代欧洲的形成

5 The Making of Modern Europe

1. B. Bramanti 等人，“地方狩猎采集者与中欧第一批农民之间的基因不连续性”，《科学》 326 (2009): 137–40。

1. B. Bramanti et al., “Genetic Discontinuity Between Local Hunter-Gatherers and Central Europe’s First Farmers,” Science 326 (2009): 137–40.

2. A. Keller 等人，“通过全基因组测序推断蒂罗尔冰人的起源和表型的新见解”，《自然通讯》 3 (2012): 698。

2. A. Keller et al., “New Insights into the Tyrolean Iceman’s Origin and Phenotype as Inferred by Whole-Genome Sequencing,” Nature Communications 3 (2012): 698.

3. W. Muller 等人，“阿尔卑斯冰人的起源和迁徙”，《科学》 302 (2003): 862–66。

3. W. Muller et al., “Origin and Migration of the Alpine Iceman,” Science 302 (2003): 862–66.

4. P. Skoglund 等人，“欧洲新石器时代农民和狩猎采集者的起源和遗传遗产”，《科学》 336 (2012): 466–69。

4. P. Skoglund et al., “Origins and Genetic Legacy of Neolithic Farmers and Hunter-Gatherers in Europe,” Science 336 (2012): 466–69.

5. Albert J. Ammerman 和 Luigi Luca Cavalli-Sforza，《新石器时代过渡与欧洲人口的遗传学》（新泽西州普林斯顿：普林斯顿大学出版社，1984 年）。

5. Albert J. Ammerman and Luigi Luca Cavalli-Sforza, The Neolithic Transition and the Genetics of Populations in Europe (Princeton, NJ: Princeton University Press, 1984).

6. NJ Patterson 等人，“人类历史上的古代混合”，遗传学192 (2012): 1065–93。

6. N. J. Patterson et al., “Ancient Admixture in Human History,” Genetics 192 (2012): 1065–93.

7. M. Raghavan 等人，“西伯利亚旧石器时代晚期基因组揭示了美洲原住民的双重祖先”，《自然》（2013 年）：doi：10.1038/nature12736。

7. M. Raghavan et al., “Upper Palaeolithic Siberian Genome Reveals Dual Ancestry of Native Americans,” Nature (2013): doi: 10.1038/nature12736.

8. I. Lazaridis 等人，“古代人类基因组表明现代欧洲人有三个祖先群体”，《自然》 513 (2014): 409–13。

8. I. Lazaridis et al., “Ancient Human Genomes Suggest Three Ancestral Populations for Present-Day Europeans,” Nature 513 (2014): 409–13.

9. C. Gamba 等人，“欧洲史前五千年横断面中的基因组流动与停滞”，《自然通讯》 5 (2014): 5257；ME Allentoft 等人，“青铜时代欧亚大陆的人口基因组学”，《自然》522 (2015): 167–72；W. Haak 等人，“来自草原的大规模迁徙是欧洲印欧语系的来源”，《自然》 522 (2015): 207–11；I. Mathieson 等人，“230 位古代欧亚人的全基因组选择模式”，《自然》 528 (2015): 499–503。

9. C. Gamba et al., “Genome Flux and Stasis in a Five Millennium Transect of European Prehistory,” Nature Communications 5 (2014): 5257; M. E. Allentoft et al., “Population Genomics of Bronze Age Eurasia,” Nature 522 (2015): 167–72; W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11; I. Mathieson et al., “Genome-Wide Patterns of Selection in 230 Ancient Eurasians,” Nature 528 (2015): 499–503.

10. Luigi Luca Cavalli-Sforza、Paolo Menozzi 和 Alberto Piazza，《人类基因的历史与地理》（新泽西州普林斯顿：普林斯顿大学出版社，1994 年）。

10. Luigi Luca Cavalli-Sforza, Paolo Menozzi, and Alberto Piazza, The History and Geography of Human Genes (Princeton, NJ: Princeton University Press, 1994).

11. Haak 等人，“大规模移民”； Mathieson 等人，“全基因组模式”。

11. Haak et al., “Massive Migration”; Mathieson et al., “Genome-Wide Patterns.”

12. Q. Fu 等人，“冰河时代欧洲的遗传历史”，《自然》 534 (2016): 200–5。

12. Q. Fu et al., “The Genetic History of Ice Age Europe,” Nature 534 (2016): 200–5.

13. I. Mathieson，“东南欧的基因组历史”，bioRxiv（2017）：doi.org/​10.1101/​135616。

13. I. Mathieson, “The Genomic History of Southeastern Europe,” bioRxiv (2017): doi.org/​10.1101/​135616.

14. K. Douka 等人，“克诺索斯遗址的年代测定及爱琴海南部最早新石器时代的到来”，《古代》 91 (2017): 304–21。

14. K. Douka et al., “Dating Knossos and the Arrival of the Earliest Neolithic in the Southern Aegean,” Antiquity 91 (2017): 304–21.

15. Haak 等人，“大规模迁徙”；M. Lipson 等人，“平行古基因组横断面揭示早期欧洲农民复杂的遗传历史”，《自然》 551 (2017): 368–72。

15. Haak et al., “Massive Migration”; M. Lipson et al., “Parallel Palaeogenomic Transects Reveal Complex Genetic History of Early European Farmers,” Nature 551 (2017): 368–72.

16. 科林·伦弗鲁，《文明之前：放射性碳革命与史前欧洲》（伦敦：乔纳森·凯普出版社，1973 年）。

16. Colin Renfrew, Before Civilization: The Radiocarbon Revolution and Prehistoric Europe (London: Jonathan Cape, 1973).

17. 玛丽亚·金布塔斯，《东欧史前史，第一部分：俄罗斯和波罗的海地区的中石器时代、新石器时代和铜器时代文化》（美国史前学院出版社）研究，哈佛大学，公告第 20 号）（马萨诸塞州剑桥：皮博迪博物馆，1956 年）。

17. Marija Gimbutas, The Prehistory of Eastern Europe, Part I: Mesolithic, Neolithic and Copper Age Cultures in Russia and the Baltic Area (American School of Prehistoric Research, Harvard University, Bulletin No. 20) (Cambridge, MA: Peabody Museum, 1956).

18. David W. Anthony，《马、轮子和语言：欧亚草原青铜时代骑手如何塑造现代世界》（新泽西州普林斯顿：普林斯顿大学出版社，2007 年）。

18. David W. Anthony, The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World (Princeton, NJ: Princeton University Press, 2007).

19. 同上。

19. Ibid.

20. 同上。

20. Ibid.

21. Haak 等人，“大规模迁移”。

21. Haak et al., “Massive Migration.”

22. 同上；I. Lazaridis 等人，“古代近东农业起源的基因组见解”，《自然》 536 (2016): 419–24。

22. Ibid.; I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24.

23. M. Ivanova，“考卡索斯与东方：Die Entstehung des 'Maikop-Phänomens' im 4. Jahrtausend v. Chr.”，Praehistorische Zeitschrift 87 (2012)：1-28。

23. M. Ivanova, “Kaukasus Und Orient: Die Entstehung des ‘Maikop-Phänomens’ im 4. Jahrtausend v. Chr.,” Praehistorische Zeitschrift 87 (2012): 1–28.

24. Haak 等人，“大规模移民”；阿伦托夫特等人，“青铜时代的欧亚大陆”。

24. Haak et al., “Massive Migration”; Allentoft et al., “Bronze Age Eurasia.”

25. 同上。

25. Ibid.

26. G. Kossinna，“Die Deutsche Ostmark：Ein Heimatboden der Germanen”，柏林（1919 年）。

26. G. Kossinna, “Die Deutsche Ostmark: Ein Heimatboden der Germanen,” Berlin (1919).

27. B. Arnold，“过去作为宣传：纳粹德国的极权主义考古学”，《古代》 64（1990）：464-78。

27. B. Arnold, “The Past as Propaganda: Totalitarian Archaeology in Nazi Germany,” Antiquity 64 (1990): 464–78.

28. H. Härke，“欧洲移民与身份的辩论”，《古代》 78（2004）：453-56。

28. H. Härke, “The Debate on Migration and Identity in Europe,” Antiquity 78 (2004): 453–56.

29. V. Heyd，“科西纳的微笑”，《古代》 91 (2017): 348–59；M. Vander Linden，“公元前三千年欧洲的人口历史：评估遗传学的贡献”，《世界考古学》 48 (2016): 714–28；NN Johannsen、G. Larson、DJ Meltzer 和 M. Vander Linden，“人类历史的综合窗口”，《科学》356 (2017): 1118–20。

29. V. Heyd, “Kossinna’s Smile,” Antiquity 91 (2017): 348–59; M. Vander Linden, “Population History in Third-Millennium-BC Europe: Assessing the Contribution of Genetics,” World Archaeology 48 (2016): 714–28; N. N. Johannsen, G. Larson, D. J. Meltzer, and M. Vander Linden, “A Composite Window into Human History,” Science 356 (2017): 1118–20.

30. Vere Gordon Childe，《雅利安人：印欧语系起源研究》（伦敦和纽约：K. Paul, Trench, Trubner and Co. 和 Alfred A. Knopf，1926 年）。

30. Vere Gordon Childe, The Aryans: A Study of Indo-European Origins (London and New York: K. Paul, Trench, Trubner and Co. and Alfred A. Knopf, 1926).

31. 哈尔克，《关于移民和身份的辩论》。

31. Härke, “Debate on Migration and Identity.”

32. Peter Bellwood，《第一批移民：全球视角下的古代移民》（英国西萨塞克斯郡奇切斯特/美国马萨诸塞州莫尔登：Wiley-Blackwell，2013 年）。

32. Peter Bellwood, First Migrants: Ancient Migration in Global Perspective (Chichester, West Sussex, UK / Malden, MA: Wiley-Blackwell, 2013).

33. Colin McEvedy 和 Richard Jones，《世界人口历史地图集》（英国米德尔塞克斯郡哈蒙兹沃思：企鹅出版社，1978 年）。

33. Colin McEvedy and Richard Jones, Atlas of World Population History (Harmondsworth, Middlesex, UK: Penguin, 1978).

34. K. Kristiansen，“印欧语系的青铜时代扩张：一个考古模型”，载于《成为欧洲人：第三个千年北欧和西欧的转型》，Christopher Prescott 和 Håkon Glørstad 编辑（牛津：Oxbow Books，2011 年），165-181 页。

34. K. Kristiansen, “The Bronze Age Expansion of Indo-European Languages: An Archaeological Model,” in Becoming European: The Transformation of Third Millennium Northern and Western Europe, ed. Christopher Prescott and Håkon Glørstad (Oxford: Oxbow Books, 2011), 165–81.

35. S. Rasmussen 等人，“ 5000 年前欧亚大陆鼠疫耶尔森菌的早期分化菌株”， Cell 163 (2015): 571–82。

35. S. Rasmussen et al., “Early Divergent Strains of Yersinia pestis in Eurasia 5,000 Years Ago,” Cell 163 (2015): 571–82.

36. AP Fitzpatrick，《埃姆斯伯里弓箭手和博斯科姆弓箭手：威尔特郡埃姆斯伯里博斯科姆丘陵的钟形杯墓葬》（英国索尔兹伯里：威塞克斯考古报告，2011 年）。

36. A. P. Fitzpatrick, The Amesbury Archer and the Boscombe Bowmen: Bell Beaker Burials at Boscombe Down, Amesbury, Wiltshire (Salisbury, UK: Wessex Archaeology Reports, 2011).

37. I. Olalde 等人，“烧杯现象和西北欧的基因组转型” ， bioRxiv (2017): doi.org/​10.1101/​135962。

37. I. Olalde et al., “The Beaker Phenomenon and the Genomic Transformation of Northwest Europe,” bioRxiv (2017): doi.org/​10.1101/​135962.

38. LM Cassidy 等人，“新石器时代和青铜时代向爱尔兰的迁徙以及岛屿大西洋基因组的建立”，美国国家科学院院刊113 (2016): 368–73。

38. L. M. Cassidy et al., “Neolithic and Bronze Age Migration to Ireland and Establishment of the Insular Atlantic Genome,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 368–73.

39. Colin Renfrew，《考古学与语言：印欧语起源之谜》（剑桥：剑桥大学出版社，1997 年）。

39. Colin Renfrew, Archaeology and Language: The Puzzle of Indo-European Origins (Cambridge: Cambridge University Press, 1997).

40. 同上。

40. Ibid.

41. P. Bellwood，“人类迁徙与主要语系的历史”，载《人类迁徙的全球史前史》（英国奇切斯特和马萨诸塞州莫尔登：Wiley-Blackwell，2013 年），第 87-95 页。

41. P. Bellwood, “Human Migrations and the Histories of Major Language Families,” in The Global Prehistory of Human Migration (Chichester, UK, and Malden, MA: Wiley-Blackwell, 2013), 87–95.

42. Renfrew，《考古学与语言》；Peter Bellwood，《第一批农民：农业社会的起源》（马萨诸塞州马尔登：布莱克威尔出版社，2005 年）。

42. Renfrew, Archaeology and Language; Peter Bellwood, First Farmers: The Origins of Agricultural Societies (Malden, MA: Blackwell, 2005).

43. Haak 等人，“大规模移民”；阿伦托夫特等人，“青铜时代的欧亚大陆”。

43. Haak et al., “Massive Migration”; Allentoft et al., “Bronze Age Eurasia.”

44. DW Anthony 和 D. Ringe，“从语言学和考古学的角度看印欧语系的故乡”，《语言学年鉴》 1（2015）：199-219。

44. D. W. Anthony and D. Ringe, “The Indo-European Homeland from Linguistic and Archaeological Perspectives,” Annual Review of Linguistics 1 (2015): 199–219.

45. 莱昂·波利亚科夫，《雅利安神话：欧洲种族主义和民族主义思想史》（纽约：基础书籍出版社，1974 年）。

45. Léon Poliakov, The Aryan Myth: A History of Racist and Nationalist Ideas in Europe (New York: Basic Books, 1974).

6 形成印度的碰撞

6 The Collision That Formed India

1. 《梨俱吠陀》， Stephanie W. Jamison 和 Joel P. Brereton 译（牛津：牛津大学出版社，2014 年），赞美诗 1.33、1.53、2.12、3.30、3.34、4.16 和 4.28。

1. The Rigveda, trans. Stephanie W. Jamison and Joel P. Brereton (Oxford: Oxford University Press, 2014), hymns 1.33, 1.53, 2.12, 3.30, 3.34, 4.16, and 4.28.

2. M. Witzel，“早期印度历史：语言和文本参数”，载于《古代南亚的印度雅利安人：语言、物质文化和种族》，George Erdosy 编（柏林：Walter de Gruyter，1995 年），第 85-125 页。

2. M. Witzel, “Early Indian History: Linguistic and Textual Parameters,” in The Indo-Aryans of Ancient South Asia: Language, Material Culture and Ethnicity, ed. George Erdosy (Berlin: Walter de Gruyter, 1995), 85–125.

3. Rita P. Wright，《古代印度河：城市化、经济和社会》（剑桥：剑桥大学出版社，2010 年）；Gregory L. Possehl，《印度河文明：当代视角》（马里兰州兰哈姆：AltaMira 出版社，2002 年）。

3. Rita P. Wright, The Ancient Indus: Urbanism, Economy, and Society (Cambridge: Cambridge University Press, 2010); Gregory L. Possehl, The Indus Civilization: A Contemporary Perspective (Lanham, MD: AltaMira Press, 2002).

4. 同上。

4. Ibid.

5. Asko Parpola，《解读印度河文字》（剑桥：剑桥大学出版社，1994 年）；S. Farmer、R. Sproat 和 M. Witzel，“印度河文字论的崩溃：哈拉帕文明识字的神话”，《吠陀研究电子期刊》 11（2004 年）：19-57。

5. Asko Parpola, Deciphering the Indus Script (Cambridge: Cambridge University Press, 1994); S. Farmer, R. Sproat, and M. Witzel, “The Collapse of the Indus-Script Thesis: The Myth of a Literate Harappan Civilization,” Electronic Journal of Vedic Studies 11 (2004): 19–57.

6. Richard H. Meadow 编，《哈拉帕遗址发掘 1986–1990：第三千年城市化的多学科方法》（威斯康星州麦迪逊：史前出版社，1991 年）；A. Lawler，“印度河崩溃：亚洲文化的终结还是开始？”，《科学》 320（2008 年）：1281–83。

6. Richard H. Meadow, ed., Harappa Excavations 1986–1990: A Multidisciplinary Approach to Third Millennium Urbanism (Madison, WI: Prehistory Press, 1991); A. Lawler, “Indus Collapse: The End or the Beginning of an Asian Culture?,” Science 320 (2008): 1281–83.

7. Jaan Puhvel，《比较神话学》（巴尔的摩：约翰·霍普金斯大学出版社，1987 年）。

7. Jaan Puhvel, Comparative Mythology (Baltimore: Johns Hopkins University Press, 1987).

8. 赖特，《古代印度河》；波塞尔，《印度河文明》。

8. Wright, The Ancient Indus; Possehl, The Indus Civilization.

9. 阿尔弗雷德·罗森伯格，《二十世纪的神话：对我们这个时代的精神与知识对抗的评估》，薇薇安·伯德译（加利福尼亚州托兰斯：正午出版社，1982 年）。

9. Alfred Rosenberg, The Myth of the Twentieth Century: An Evaluation of the Spiritual-Intellectual Confrontations of Our Age, trans. Vivian Bird (Torrance, CA: Noontide Press, 1982).

10. 莱昂·波利亚科夫，《雅利安神话：欧洲种族主义和民族主义思想史》（纽约：基础书籍出版社，1974 年）。

10. Léon Poliakov, The Aryan Myth: A History of Racist and Nationalist Ideas in Europe (New York: Basic Books, 1974).

11. B. Arnold，“过去作为宣传：纳粹德国的极权主义考古学”，《古代》 64（1990）：464-78。

11. B. Arnold, “The Past as Propaganda: Totalitarian Archaeology in Nazi Germany,” Antiquity 64 (1990): 464–78.

12. Bryan Ward-Perkis，《罗马的衰落与文明的终结》（牛津：牛津大学出版社，2005 年）。

12. Bryan Ward-Perkis, The Fall of Rome and the End of Civilization (Oxford: Oxford University Press, 2005).

13. Peter Bellwood，《第一批农民：农业社会的起源》（马萨诸塞州马尔登：布莱克威尔出版社，2005 年）。

13. Peter Bellwood, First Farmers: The Origins of Agricultural Societies (Malden, MA: Blackwell, 2005).

14. 同上。

14. Ibid.

15. M. Witzel，“古印度雅利安语（梨俱吠陀语、中期吠陀语和晚期吠陀语）中的底层语言”，《吠陀研究电子期刊》 5（1999）：1-67。

15. M. Witzel, “Substrate Languages in Old Indo-Aryan (Rgvedic, Middle and Late Vedic),” Electronic Journal of Vedic Studies 5 (1999): 1–67.

16. K. Thangaraj 等人，“重建安达曼岛民的起源”，《科学》 308 (2005): 996；K. Thangaraj 等人，“印度线粒体宏单倍群‘M’深根谱系的原位起源”， 《BMC基因组学》 7 (2006): 151。

16. K. Thangaraj et al., “Reconstructing the Origin of Andaman Islanders,” Science 308 (2005): 996; K. Thangaraj et al., “In situ Origin of Deep Rooting Lineages of Mitochondrial Macrohaplogroup ‘M’ in India,” BMC Genomics 7 (2006): 151.

17. RS Wells 等人，“欧亚大陆中心地带：Y 染色体多样性的大陆视角”，《美国国家科学院院刊》 98 (2001): 10244–49；M. Bamshad 等人，“印度种姓人口起源的遗传证据”，《基因组研究》11 (2001): 994–1004；I. Thanseem 等人，“印度低种姓和部落群体之间的遗传亲缘关系：来自 Y 染色体和线粒体 DNA 的推断”，《BMC 遗传学》 7 (2006): 42。

17. R. S. Wells et al., “The Eurasian Heartland: A Continental Perspective on Y-chromosome Diversity,” Proceedings of the National Academy of Sciences of the U.S.A. 98 (2001): 10244–49; M. Bamshad et al., “Genetic Evidence on the Origins of Indian Caste Populations,” Genome Research 11 (2001): 994–1004; I. Thanseem et al., “Genetic Affinities Among the Lower Castes and Tribal Groups of India: Inference from Y Chromosome and Mitochondrial DNA,” BMC Genetics 7 (2006): 42.

18. Thangaraj 等人，“安达曼岛民”。

18. Thangaraj et al., “Andaman Islanders.”

19. D. Reich 等人，“重建印度人口历史”，《自然》 461（2009）：489-94。

19. D. Reich et al., “Reconstructing Indian Population History,” Nature 461 (2009): 489–94.

20. RE Green 等人，“尼安德特人基因组草图序列”，《科学》 328 (2010): 710–22。

20. R. E. Green et al., “A Draft Sequence of the Neandertal Genome,” Science 328 (2010): 710–22.

21. Thangaraj 等人，“根深蒂固的血统”。

21. Thangaraj et al., “Deep Rooting Lineages.”

22. Reich 等人，“重建印度人口历史”；P. Moorjani 等人，“印度近期人口混合的遗传证据”，《美国人类遗传学杂志》 93 (2013): 422–38。

22. Reich et al., “Reconstructing Indian Population History”; P. Moorjani et al., “Genetic Evidence for Recent Population Mixture in India,” American Journal of Human Genetics 93 (2013): 422–38.

23. 同上。

23. Ibid.

24. 伊拉瓦蒂·卡尔维，《印度教社会——一种诠释》（印度浦那：德干学院研究生和研究学院，1961 年）。

24. Irawati Karve, Hindu Society—An Interpretation (Pune, India: Deccan College Post Graduate and Research Institute, 1961).

25. PA Underhill 等人，“Y 染色体单倍群 R1a 的系统发育和地理结构”，《欧洲人类遗传学杂志》 23 (2015): 124–31。

25. P. A. Underhill et al., “The Phylogenetic and Geographic Structure of Y-Chromosome Haplogroup R1a,” European Journal of Human Genetics 23 (2015): 124–31.

26. S. Perur，“印度人的起源：我们的基因告诉我们什么”，Fountain Ink， 2013 年 12 月 3 日，http://fountainink.in/​?p=4669&all=1。

26. S. Perur, “The Origins of Indians: What Our Genes Are Telling Us,” Fountain Ink, December 3, 2013, http://fountainink.in/​?p=4669&all=1.

27. K. Bryc 等人，“美国各地非裔美国人、拉丁裔美国人和欧裔美国人的遗传祖先”，《美国人类遗传学杂志》 96 (2015): 37–53。

27. K. Bryc et al., “The Genetic Ancestry of African Americans, Latinos, and European Americans Across the United States,” American Journal of Human Genetics 96 (2015): 37–53.

28. LG Carvajal-Carmona 等人，“哥伦比亚西北部一个人口的创始人中强烈的美洲印第安人/白人性别偏向和可能的塞法迪犹太人贡献”，《美国人类遗传学杂志》 67 (2000): 1287–95；G. Bedoya 等人，“西班牙裔的混合动态：南美洲一个孤立人口的核遗传祖先的转变”，《美国国家科学院院刊》 103 (2006): 7234–39。

28. L. G. Carvajal-Carmona et al., “Strong Amerind/White Sex Bias and a Possible Sephardic Contribution Among the Founders of a Population in Northwest Colombia,” American Journal of Human Genetics 67 (2000): 1287–95; G. Bedoya et al., “Admixture Dynamics in Hispanics: A Shift in the Nuclear Genetic Ancestry of a South American Population Isolate,” Proceedings of the National Academy of Sciences of the U.S.A. 103 (2006): 7234–39.

29. Moorjani 等人，“近期人口混合”。

29. Moorjani et al., “Recent Population Mixture.”

30. 同上。

30. Ibid.

31. Romila Thapar，《早期印度：从起源到公元 1300 年》（伯克利：加州大学出版社，2002 年）；Karve，《印度教社会》； Susan Bayly，《从十八世纪到现代的印度种姓、社会和政治》（剑桥：剑桥大学出版社，1999 年）；MN Srinivas，《现代印度的种姓及其他论文》（孟买：亚洲出版社，1962 年）；Louis Dumont，《等级人：种姓制度及其影响》（芝加哥：芝加哥大学出版社，1980 年）。

31. Romila Thapar, Early India: From the Origins to AD 1300 (Berkeley: University of California Press, 2002); Karve, Hindu Society; Susan Bayly, Caste, Society and Politics in India from the Eighteenth Century to the Modern Age (Cambridge: Cambridge University Press, 1999); M. N. Srinivas, Caste in Modern India and Other Essays (Bombay: Asia Publishing House, 1962); Louis Dumont, Homo Hierarchicus: The Caste System and Its Implications (Chicago: University of Chicago Press, 1980).

32. Kumar Suresh Singh，《印度人民：导论》（印度人民国家系列）（新德里：牛津大学出版社，2002）；KC Malhotra 和 TS Vasulu，“印度人口结构”，载《人类人口遗传学》ics：JBS Haldane 百年纪念文集， Partha P. Majumder 编辑（纽约：Plenum Press，1993 年），207-34 页。

32. Kumar Suresh Singh, People of India: An Introduction (People of India National Series) (New Delhi: Oxford University Press, 2002); K. C. Malhotra and T. S. Vasulu, “Structure of Human Populations in India,” in Human Population Genetics: A Centennial Tribute to J. B. S. Haldane, ed. Partha P. Majumder (New York: Plenum Press, 1993), 207–34.

33. 卡尔维，《印度教社会》。

33. Karve, “Hindu Society.”

34. 同上。

34. Ibid.

35. Nicholas B. Dirks，《种姓的思维：殖民主义与现代印度的形成》（新泽西州普林斯顿：普林斯顿大学出版社，2001 年）；N. Boivin，“南亚种姓起源的人类学、历史学、考古学和遗传学视角”，载于Michael D. Petraglia 和 Bridget Allchin 编辑的《南亚人口的演变与历史》（荷兰多德雷赫特：施普林格出版社，2007 年），第 341-362 页。

35. Nicholas B. Dirks, Castes of Mind: Colonialism and the Making of Modern India (Princeton, NJ: Princeton University Press, 2001); N. Boivin, “Anthropological, Historical, Archaeological and Genetic Perspectives on the Origins of Caste in South Asia,” in The Evolution and History of Human Populations in South Asia, ed. Michael D. Petraglia and Bridget Allchin (Dordrecht, The Netherlands: Springer, 2007), 341–62.

36. Reich 等人，“重建印度人口历史”。

36. Reich et al., “Reconstructing Indian Population History.”

37. M. Arcos-Burgos 和 M. Muenke，“群体隔离的遗传学”，临床遗传学61 (2002): 233–47。

37. M. Arcos-Burgos and M. Muenke, “Genetics of Population Isolates,” Clinical Genetics 61 (2002): 233–47.

38. N. Nakatsuka 等人，“在南亚发现特定人群疾病相关基因的前景”，《自然遗传学》 49 (2017): 1403–7。

38. N. Nakatsuka et al., “The Promise of Discovering Population-Specific Disease-Associated Genes in South Asia,” Nature Genetics 49 (2017): 1403–7.

39. Reich 等人，“重建印度人口历史”。

39. Reich et al., “Reconstructing Indian Population History.”

40. I. Manoharan 等人，“印度 Vysya 社区中人类丁酰胆碱酯酶的自然发生突变 Leu307Pro”，药物遗传学和基因组学16 (2006)：461–68。

40. I. Manoharan et al., “Naturally Occurring Mutation Leu307Pro of Human Butyr​ylcho​lines​teras​e in the Vysya Community of India,” Pharmacogenetics and Genomics 16 (2006): 461–68.

41. AE Raz，“基于人群的携带者筛查能否交给社区？”，《遗传咨询杂志》 18（2009）：114-18。

41. A. E. Raz, “Can Population-Based Carrier Screening Be Left to the Community?,” Journal of Genetic Counseling 18 (2009): 114–18.

42. I. Lazaridis 等人，“古代近东农业起源的基因组见解”，《自然》 536 (2016): 419–24；F. Broushaki 等人，“来自东部肥沃新月地带的早期新石器时代基因组”，《科学》 353 (2016): 499–503。

42. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24; F. Broushaki et al., “Early Neolithic Genomes from the Eastern Fertile Crescent,” Science 353 (2016): 499–503.

43. 同上。

43. Ibid.

44. Lazaridis 等人，“基因组学见解”。

44. Lazaridis et al., “Genomic Insights.”

45. 来自大卫·赖希实验室的未发表结果。

45. Unpublished results from David Reich’s laboratory.

7 寻找美洲原住民祖先

7 In Search of Native American Ancestors

1. Betty Mindlin，《朗多尼亚苏鲁伊印第安人的未书写的故事》（奥斯汀：拉丁美洲研究所；德克萨斯大学出版社发行，1995 年）。

1. Betty Mindlin, Unwritten Stories of the Suruí Indians of Rondônia (Austin: Institute of Latin American Studies; distributed by the University of Texas Press, 1995).

2. D. Reich 等人，“重建美洲原住民人口历史”，《自然》 488 (2012): 370–74。

2. D. Reich et al., “Reconstructing Native American Population History,” Nature 488 (2012): 370–74.

3. P. Skoglund 等人，“美洲两个创始种群的遗传证据”，《自然》 525 (2015): 104–8。

3. P. Skoglund et al., “Genetic Evidence for Two Founding Populations of the Americas,” Nature 525 (2015): 104–8.

4. PD Heintzman 等人，“野牛系统地理学限制了加拿大西部无冰走廊的扩散和生存能力”，美国国家科学院院刊113 (2016): 8057–63；MW Pedersen 等人，“北美无冰走廊的冰后期生存能力和殖民化”，自然537 (2016): 45–49。

4. P. D. Heintzman et al., “Bison Phylogeography Constrains Dispersal and Viability of the Ice Free Corridor in Western Canada,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 8057–63; M. W. Pedersen et al., “Postglacial Viability and Colonization in North America’s Ice-Free Corridor,” Nature 537 (2016): 45–49.

5. 何塞·德·阿科斯塔，《印度的自然与道德史：En que se Tratan las Cosas Notables del Cielo y Elementos, Metales, Plantas y Animales de Ellas y los Ritos, Ceremonias, Leyes y Gobierno y Guerras de los Indios》（塞维利亚：胡安·德莱昂，1590）。

5. José de Acosta, Historia Natural y Moral de las Indias: En que se Tratan las Cosas Notables del Cielo y Elementos, Metales, Plantas y Animales de Ellas y los Ritos, Ceremonias, Leyes y Gobierno y Guerras de los Indios (Seville: Juan de León, 1590).

6. David J. Meltzer，《新世界的第一批居民：殖民冰河时代的美国》（伯克利：加州大学出版社，2009 年）。

6. David J. Meltzer, First Peoples in a New World: Colonizing Ice Age America (Berkeley: University of California Press, 2009).

7. JH Greenberg、CG Turner II 和 SL Zegura，“美洲的定居：语言学、牙齿学和遗传学证据的比较”，当代人类学27 (1986): 477–97。

7. J. H. Greenberg, C. G. Turner II, and S. L. Zegura, “The Settlement of the Americas: A Comparison of the Linguistic, Dental, and Genetic Evidence,” Current Anthropology 27 (1986): 477–97.

8. P. Forster、R. Harding、A. Torroni 和 H.-J. Bandelt，“美洲原住民线粒体 DNA 变异的起源和演化：重新评估”，《美国人类遗传学杂志》 59 (1996): 935–45；E. Tamm 等人，“白令海峡停滞和美洲原住民创始人的传播”，《公共科学图书馆·综合》 2 (2017): e829。

8. P. Forster, R. Harding, A. Torroni, and H.-J. Bandelt, “Origin and Evolution of Native American mtDNA Variation: A Reappraisal,” American Journal of Human Genetics 59 (1996): 935–45; E. Tamm et al., “Beringian Standstill and Spread of Native American Founders,” PloS One 2 (2017): e829.

9. TD Dillehay 等人，“蒙特维德：海藻、食物、药物和南美洲的人口迁徙”，《科学》 320 (2008): 784–86。

9. T. D. Dillehay et al., “Monte Verde: Seaweed, Food, Medicine, and the Peopling of South America,” Science 320 (2008): 784–86.

10. DL Jenkins 等人，“佩斯利洞穴中的克洛维斯时代西部带柄投射点和人类粪化石”，《科学》 337 (2012): 223–28。

10. D. L. Jenkins et al., “Clovis Age Western Stemmed Projectile Points and Human Coprolites at the Paisley Caves,” Science 337 (2012): 223–28.

11. M. Rasmussen 等人，“来自蒙大拿州西部克洛维斯墓地的晚更新世人类基因组”，《自然》 506 (2014): 225–29。

11. M. Rasmussen et al., “The Genome of a Late Pleistocene Human from a Clovis Burial Site in Western Montana,” Nature 506 (2014): 225–29.

12. Povos Indígenas No Brasil，“Karitiana：生物盗版和未经授权的生物医学样本收集”，https://pib.socioambiental.org/​en/​povo/​karitiana/​389。

12. Povos Indígenas No Brasil, “Karitiana: Biopiracy and the Unauthorized Collection of Biomedical Samples,” https://pib.socioambiental.org/​en/​povo/​karitiana/​389.

13. NA Garrison 和 MK Cho，“意识和可接受的做法：IRB 和研究人员对 Havasupai 诉讼的反思”，AJOB 初级研究4 (2013): 55–63；A. Harmon，“印第安部落赢得限制对其 DNA 研究的斗争”，《纽约时报》， 2010 年 4 月 21 日。

13. N. A. Garrison and M. K. Cho, “Awareness and Acceptable Practices: IRB and Researcher Reflections on the Havasupai Lawsuit,” AJOB Primary Research 4 (2013): 55–63; A. Harmon, “Indian Tribe Wins Fight to Limit Research of Its DNA,” New York Times, April 21, 2010.

14. Ronald P. Maldonado，“大学研究人员在考虑与纳瓦霍族开展研究项目时的关键点”，http://nptao.arizona.edu/​sites/​nptao/​files/​navaj​onat​onkey​researchre​quire​ments_0.pdf。

14. Ronald P. Maldonado, “Key Points for University Researchers When Considering a Research Project with the Navajo Nation,” http://nptao.arizona.edu/​sites/​nptao/​files/​navaj​onati​onkey​resea​rchre​quire​ments_0.pdf.

15. Rebecca Skloot，《亨丽埃塔·拉克斯的永生》（纽约：皇冠出版社，2010 年）。

15. Rebecca Skloot, The Immortal Life of Henrietta Lacks (New York: Crown, 2010).

16. BL Shelton，“美国印第安人和阿拉斯加原住民基因研究中的同意和咨询”，http://www.ipcb.org/​publications/​briefing_papers/​files/​consent.html。

16. B. L. Shelton, “Consent and Consultation in Genetic Research on American Indians and Alaska Natives,” http://www.ipcb.org/​publications/​briefing_papers/​files/​consent.html.

17. RR Sharp 和 MW Foster，“让研究人群参与遗传研究的审查”，《法律、医学和伦理杂志》28 (2000): 41–51；国际 HapMap 联盟，“国际 HapMap 项目”，《自然》 426 (2003): 789–96。

17. R. R. Sharp and M. W. Foster, “Involving Study Populations in the Review of Genetic Research,” Journal of Law, Medicine and Ethics 28 (2000): 41–51; International HapMap Consortium, “The International HapMap Project,” Nature 426 (2003): 789–96.

18. T. Egan，“部落停止对挑战历史的骨骼的研究”，《纽约时报》， 1996 年 9 月 30 日；Douglas W. Owsley 和 Richard L. Jantz，《肯纳威克人：对古代美洲骨骼的科学调查》（大学城：德克萨斯农工大学出版社，2014 年）；DJ Meltzer，“肯纳威克人：即将结束”， 《古代》 348（2015 年）：1485–93。

18. T. Egan, “Tribe Stops Study of Bones That Challenge History,” New York Times, September 30, 1996; Douglas W. Owsley and Richard L. Jantz, Kennewick Man: The Scientific Investigation of an Ancient American Skeleton (College Station: Texas A&M University Press, 2014); D. J. Meltzer, “Kennewick Man: Coming to Closure,” Antiquity 348 (2015): 1485–93.

19. M. Rasmussen 等人，“肯纳威克人的祖先和归属”，《自然》 523 (2015): 455–58。

19. M. Rasmussen et al., “The Ancestry and Affiliations of Kennewick Man,” Nature 523 (2015): 455–58.

20. 同上。

20. Ibid.

21. J. Lindo 等人，“来自北美西北海岸的古代个体揭示了 10,000 年的区域遗传连续性”，美国国家科学院院刊114 (2017): 4093–98。

21. J. Lindo et al., “Ancient Individuals from the North American Northwest Coast Reveal 10,000 Years of Regional Genetic Continuity,” Proceedings of the National Academy of Sciences of the U.S.A. 114 (2017): 4093–98.

22. Samuel J. Redman，《骨骼房间：从科学种族主义到博物馆中的人类史前史》（马萨诸塞州剑桥和伦敦：哈佛大学出版社，2016 年）。

22. Samuel J. Redman, Bone Rooms: From Scientific Racism to Human Prehistory in Museums (Cambridge, MA, and London: Harvard University Press, 2016).

23. M. Rasmussen 等人，“澳大利亚原住民基因组揭示了人类向亚洲的独立扩散”，《科学》 334 (2011): 94–98。

23. M. Rasmussen et al., “An Aboriginal Australian Genome Reveals Separate Human Dispersals into Asia,” Science 334 (2011): 94–98.

24. Rasmussen 等人，“晚更新世人类基因组”。

24. Rasmussen et al., “Genome of a Late Pleistocene Human.”

25. Rasmussen 等人，“肯纳威克人的祖先和归属”。

25. Rasmussen et al., “Ancestry and Affiliations of Kennewick Man.”

26. AS Malaspinas 等人，“澳大利亚原住民的基因组历史”，《自然》 538 (2016): 207–14。

26. A. S. Malaspinas et al., “A Genomic History of Aboriginal Australia,” Nature 538 (2016): 207–14.

27. E. Callaway，“古代基因组为美国部落带来‘灵魂洞穴木乃伊’”，《自然》 540（2016）：178-79。

27. E. Callaway, “Ancient Genome Delivers ‘Spirit Cave Mummy’ to US tribe,” Nature 540 (2016): 178–79.

28. 同上。

28. Ibid.

29. M. Livi-Bacci，“征服后西班牙裔美洲的人口减少”，《人口与发展评论》 32（2006）：199-232；Lewis H. Morgan，《古代社会；或从野蛮到文明的人类进步路线研究》（芝加哥：Charles H. Kerr，1909）。

29. M. Livi-Bacci, “The Depopulation of Hispanic America After the Conquest,” Population and Development Review 32 (2006): 199–232; Lewis H. Morgan, Ancient Society; Or, Researches in the Lines of Human Progress from Savagery Through Barbarism to Civilization (Chicago: Charles H. Kerr, 1909).

30. Reich 等人，“重建美洲原住民人口历史”。

30. Reich et al., “Reconstructing Native American Population History.”

31. Lindo 等人，“古代个体”。

31. Lindo et al., “Ancient Individuals.”

32. Lyle Campbell 和 Marianne Mithun，《美洲原住民语言：历史与比较评估》（奥斯汀：德克萨斯大学出版社，1979 年）。

32. Lyle Campbell and Marianne Mithun, The Languages of Native America: Historical and Comparative Assessment (Austin: University of Texas Press, 1979).

33. L. Campbell，“对 Greenberg、Turner 和 Zegura 的评论”，当代人类学27 (1986): 488。

33. L. Campbell, “Comment on Greenberg, Turner and Zegura,” Current Anthropology 27 (1986): 488.

34. Peter Bellwood，《第一批移民：全球视角下的古代移民》（英国西萨塞克斯郡奇切斯特/美国马萨诸塞州莫尔登：Wiley-Blackwell，2013 年）。

34. Peter Bellwood, First Migrants: Ancient Migration in Global Perspective (Chichester, West Sussex, UK / Malden, MA: Wiley-Blackwell, 2013).

35. Reich 等人，“重建美洲原住民人口历史”。

35. Reich et al., “Reconstructing Native American Population History.”

36. WA Neves 和 M. Hubbe，“来自巴西圣塔湖的早期美洲人的颅骨形态：对新世界定居的启示”，美国国家科学院院刊102 (2005): 18309–14。

36. W. A. Neves and M. Hubbe, “Cranial Morphology of Early Americans from Lagoa Santa, Brazil: Implications for the Settlement of the New World,” Proceedings of the National Academy of Sciences of the U.S.A. 102 (2005): 18309–14.

37. Rasmussen 等人，“肯纳威克人的祖先和归属”。

37. Rasmussen et al., “Ancestry and Affiliations of Kennewick Man.”

38. P. Skoglund 等人，“美洲两个创始种群的遗传证据”，《自然》 525 (2015): 104–8。

38. P. Skoglund et al., “Genetic Evidence for Two Founding Populations of the Americas,” Nature 525 (2015): 104–8.

39. 巴西土著人民，“苏鲁伊·派特：简介”，https://pib.socioambiental.org/​en/​povo/​surui-paiter；RA Butler，“亚马逊印第安人使用谷歌地球和GPS保护森林家园”，Mongabay：来自自然前线的新闻和灵感， 2006年11月15日，https://news.mongabay.com/​2006/​11/​amazon-indians-use-google-earth-gps-to-protect-forest-home/。

39. Povos Indígenas No Brasil, “Surui Paiter: Introduction,” https://pib.socioambiental.org/​en/​povo/​surui-paiter; R. A. Butler, “Amazon Indians Use Google Earth, GPS to Protect Forest Home,” Mongabay: News and Inspiration from Nature’s Frontline, November 15, 2006, https://news.mongabay.com/​2006/​11/​amazon-indians-use-google-earth-gps-to-protect-forest-home/.

40. “卡里蒂亚纳：生物剽窃和未经授权的采集。”

40. “Karitiana: Biopiracy and the Unauthorized Collection.”

41. Povos Indígenas No Brasil，“Xavante：简介”，https://pib.socioambiental.org/en/povo/xavante。

41. Povos Indígenas No Brasil, “Xavante: Introduction,” https://pib.socioambiental.org/​en/​povo/​xavante.

42. M. Raghavan 等人，“美洲原住民更新世和近期人口历史的基因组证据”，《科学》 349 (2015): aab3884。

42. M. Raghavan et al., “Genomic Evidence for the Pleistocene and Recent Population History of Native Americans,” Science 349 (2015): aab3884.

43. EJ Vajda，“西伯利亚与纳德内语系的联系”，载于《阿拉斯加大学人类学论文集：新系列》， James M. Kari 和 Ben Austin Potter 编辑，5 (2010)：33–99。

43. E. J. Vajda, “A Siberian Link with Na-Dene Languages,” in Anthropological Papers of the University of Alaska: New Series, ed. James M. Kari and Ben Austin Potter, 5 (2010): 33–99.

44. Reich 等人，“重建美洲原住民人口历史”。

44. Reich et al., “Reconstructing Native American Population History.”

45. M. Rasmussen 等人，“已灭绝的古爱斯基摩人的古代人类基因组序列”，《自然》 463 (2010): 757–62。

45. M. Rasmussen et al., “Ancient Human Genome Sequence of an Extinct Palaeo-Eskimo,” Nature 463 (2010): 757–62.

46. M. Raghavan 等人，“新世界北极的遗传史前史”，《科学》 345 (2014): 1255832。

46. M. Raghavan et al., “The Genetic Prehistory of the New World Arctic,” Science 345 (2014): 1255832.

47. P. Flegontov 等人，“北美古爱斯基摩遗传遗产”，bioRxiv (2017)：doi.org/10.1101/203018。

47. P. Flegontov et al., “Paleo-Eskimo Genetic Legacy Across North America,” bioRxiv (2017): doi.org/​10.1101/​203018.

48. Flegontov 等人，“古爱斯基摩人的遗传遗产”。

48. Flegontov et al., “Paleo-Eskimo Genetic Legacy.”

49. TM Friesen，“泛北极人口迁徙：早期古因纽特人和图勒因纽特人的迁徙”，载于《牛津史前北极手册》， T. Max Friesen 和 Owen K. Mason 编辑（纽约：牛津大学出版社，2016 年），第 673-92 页。

49. T. M. Friesen, “Pan-Arctic Population Movements: The Early Paleo-Inuit and Thule Inuit Migrations,” in The Oxford Handbook of the Prehistoric Arctic, ed. T. Max Friesen and Owen K. Mason (New York: Oxford University Press, 2016), 673–92.

50. Reich 等人，“重建美洲原住民人口历史”。

50. Reich et al., “Reconstructing Native American Population History.”

51. J. Diamond 和 P. Bellwood，“农民及其语言：最初的扩张”，《科学》 300 (2003): 597–603；Peter Bellwood，《第一批农民：农业社会的起源》（马萨诸塞州马尔登：布莱克威尔出版社，2005 年）。

51. J. Diamond and P. Bellwood, “Farmers and Their Languages: The First Expansions,” Science 300 (2003): 597–603; Peter Bellwood, First Farmers: The Origins of Agricultural Societies (Malden, MA: Blackwell, 2005).

52. RR da Fonseca 等人，“美国西南部玉米的起源和演化”，《自然植物》 1（2015）：14003。

52. R. R. da Fonseca et al., “The Origin and Evolution of Maize in the Southwestern United States,” Nature Plants 1 (2015): 14003.

8 东亚人的基因组起源

8 The Genomic Origins of East Asians

1. XH Wu 等，“中国仙人洞两万年前的早期陶器”，《科学》 336 (2012): 1696–1700。

1. X. H. Wu et al., “Early Pottery at 20,000 Years Ago in Xianrendong Cave, China,” Science 336 (2012): 1696–1700.

2. 朱瑞祥等，“东亚人属的早期证据”， 《人类进化杂志》 55（2008）：1075-85。

2. R. X. Zhu et al., “Early Evidence of the Genus Homo in East Asia,” Journal of Human Evolution 55 (2008): 1075–85.

3. CC Swisher III 等人，“印度尼西亚爪哇岛已知最早的人类的年龄”，《科学》 263 (1994): 1118–21；Peter Bellwood，《第一批岛民：东南亚岛屿的史前史和人类迁徙》（牛津：Wiley-Blackwell，2017）。

3. C. C. Swisher III et al., “Age of the Earliest Known Hominids in Java, Indonesia,” Science 263 (1994): 1118–21; Peter Bellwood, First Islanders: Prehistory and Human Migration in Island Southeast Asia (Oxford: Wiley-Blackwell, 2017).

4. D. Richter 等人，“摩洛哥 Jebel Irhoud 古人类化石的时代和中石器时代的起源”，Nature 546 (2017)：293-96； JG Fleagle、Z. Assefa、FH Brown 和 JJ Shea，“埃塞俄比亚南部基比什地层的古人类学：简介”，人类进化杂志55 (2008)：360-65。

4. D. Richter et al., “The Age of the Hominin Fossils from Jebel Irhoud, Morocco, and the Origins of the Middle Stone Age,” Nature 546 (2017): 293–96; J. G. Fleagle, Z. Assefa, F. H. Brown, and J. J. Shea, “Paleoanthropology of the Kibish Formation, Southern Ethiopia: Introduction,” Journal of Human Evolution 55 (2008): 360–65.

5. T. Sutikna 等人，“印度尼西亚梁布亚人地层学和年代学的修订”， 《自然》 532 (2016): 366–69。

5. T. Sutikna et al., “Revised Stratigraphy and Chronology for Homo floresiensis at Liang Bua in Indonesia,” Nature 532 (2016): 366–69.

6. Y. Ke 等人，“现代人类起源于东亚的非洲：12,000 个 Y 染色体的故事”，《科学》 292 (2001): 1151–53。

6. Y. Ke et al., “African Origin of Modern Humans in East Asia: A Tale of 12,000 Y Chromosomes,” Science 292 (2001): 1151–53.

7. J. Qiu，“被遗忘的大陆：中国的化石发现挑战了关于现代人类及其近亲进化的观点”，《自然》 535（2016）：218-20。

7. J. Qiu, “The Forgotten Continent: Fossil Finds in China Are Challenging Ideas About the Evolution of Modern Humans and Our Closest Relatives,” Nature 535 (2016): 218–20.

8. RJ Rabett 和 PJ Piper，“东南亚更新世末期骨技术的出现：区域和演化意义”，《剑桥考古学杂志》 22 (2012): 37–56；MC Langley、C. Clarkson 和 S. Ulm，“从小孔到宏大叙事：埋藏学和样本量对澳大利亚和新几内亚现代性辩论的影响”， 《人类进化杂志》 61 (2011): 197–208；M. Aubert 等，“印度尼西亚苏拉威西岛的更新世洞穴艺术”，《自然》 514 (2014): 223–27。

8. R. J. Rabett and P. J. Piper, “The Emergence of Bone Technologies at the End of the Pleistocene in Southeast Asia: Regional and Evolutionary Implications,” Cambridge Archaeological Journal 22 (2012): 37–56; M. C. Langley, C. Clarkson, and S. Ulm, “From Small Holes to Grand Narratives: The Impact of Taphonomy and Sample Size on the Modernity Debate in Australia and New Guinea,” Journal of Human Evolution 61 (2011): 197–208; M. Aubert et al., “Pleistocene Cave Art from Sulawesi, Indonesia,” Nature 514 (2014): 223–27.

9. Langley、Clarkson 和 Ulm，“从小洞到宏大叙事”；JF Connell 和 J. Allen，“大约 47,000 年前人类殖民萨胡尔的过程、生物影响和全球意义”，《考古科学杂志》 56 (2015): 73–84。

9. Langley, Clarkson, and Ulm, “From Small Holes to Grand Narratives”; J. F. Connell and J. Allen, “The Process, Biotic Impact, and Global Implications of the Human Colonization of Sahul About 47,000 Years Ago,” Journal of Archaeological Science 56 (2015): 73–84.

10. J.-J. Hublin，“现代人类对西欧亚大陆的殖民：何时何地？”，第四纪科学评论118 (2015): 194–210。

10. J.-J. Hublin, “The Modern Human Colonization of Western Eurasia: When and Where?,” Quaternary Science Reviews 118 (2015): 194–210.

11. R. Foley 和 MM Lahr，“模式 3 技术与现代人类的进化”，剑桥考古杂志7 (1997): 3–36。

11. R. Foley and M. M. Lahr, “Mode 3 Technologies and the Evolution of Modern Humans,” Cambridge Archaeological Journal 7 (1997): 3–36.

12. MM Lahr 和 R. Foley，“多次扩散和现代人类起源”，进化人类学3 (1994): 48–60。

12. M. M. Lahr and R. Foley, “Multiple Dispersals and Modern Human Origins,” Evolutionary Anthropology 3 (1994): 48–60.

13. H. Reyes-Centeno 等人，“检验现代人类走出非洲的扩散模型及其对现代人类起源的影响”，《人类进化杂志》 87 (2015): 95–106。

13. H. Reyes-Centeno et al., “Testing Modern Human Out-of-Africa Dispersal Models and Implications for Modern Human Origins,” Journal of Human Evolution 87 (2015): 95–106.

14. HS Groucutt 等人，“重新思考智人走出非洲的扩散”，进化人类学24 (2015): 149–64。

14. H. S. Groucutt et al., “Rethinking the Dispersal of Homo sapiens Out of Africa,” Evolutionary Anthropology 24 (2015): 149–64.

15. R. Grün 等人，“与斯库尔人类墓葬相关的骨骼和牙齿的 U 系列和 ESR 分析”，《人类进化杂志》 49 (2005): 316–34。

15. R. Grün et al., “U-series and ESR Analyses of Bones and Teeth Relating to the Human Burials from Skhul,” Journal of Human Evolution 49 (2005): 316–34.

16. SJ Armitage 等人，“走出非洲的南部路线：现代人类早期向阿拉伯扩张的证据”，《科学》 331 (2011): 453–56；MD Petraglia，“非洲的开拓者”，《自然》 470 (2011): 50–51。

16. S. J. Armitage et al., “The Southern Route ‘Out of Africa’: Evidence for an Early Expansion of Modern Humans into Arabia,” Science 331 (2011): 453–56; M. D. Petraglia, “Trailblazers Across Africa,” Nature 470 (2011): 50–51.

17. M. Kuhlwilm 等人，“早期现代人类向东部尼安德特人的古代基因流动”，《自然》 530 (2016): 429–33。

17. M. Kuhlwilm et al., “Ancient Gene Flow from Early Modern Humans into Eastern Neanderthals,” Nature 530 (2016): 429–33.

18. M. Rasmussen 等人，“澳大利亚原住民基因组揭示了人类向亚洲的独立扩散”，《科学》 334 (2011): 94–98。

18. M. Rasmussen et al., “An Aboriginal Australian Genome Reveals Separate Human Dispersals into Asia,” Science 334 (2011): 94–98.

19. D. Reich 等人，“西伯利亚丹尼索瓦洞穴中古人类群体的遗传历史”，《自然》 468 (2010): 1053–60；M. Meyer 等人，“来自古丹尼索瓦个体的高覆盖率基因组序列”，《科学》 338 (2012): 222–26。

19. D. Reich et al., “Genetic History of an Archaic Hominin Group from Denisova Cave in Siberia,” Nature 468 (2010): 1053–60; M. Meyer et al., “A High-Coverage Genome Sequence from an Archaic Denisovan Individual,” Science 338 (2012): 222–26.

20. S. Mallick 等人，“西蒙斯基因组多样性计划：来自 142 个不同种群的 300 个基因组”，《自然》 538 (2016)：201-6。

20. S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6.

21. Q. Fu 等人，“来自西伯利亚西部的 45,000 年前现代人类的基因组序列”，《自然》 514 (2014): 445–49；S. Sankararaman、S. Mallick、N. Patterson 和 D. Reich，“现代人类中丹尼索瓦人和尼安德特人祖先的综合图景”，《当代生物学》 26 (2016): 1241–47；P. Moorjani 等人，“一种用于测定古代基因组年代的遗传方法提供了过去 45,000 年人类世代间隔的直接估计”，《美国国家科学院院刊》 113 (2016): 5652–7。

21. Q. Fu et al., “Genome Sequence of a 45,000-Year-Old Modern Human from Western Siberia,” Nature 514 (2014): 445–49; S. Sankararaman, S. Mallick, N. Patterson, and D. Reich, “The Combined Landscape of Denisovan and Neanderthal Ancestry in Present-Day Humans,” Current Biology 26 (2016): 1241–47; P. Moorjani et al., “A Genetic Method for Dating Ancient Genomes Provides a Direct Estimate of Human Generation Interval in the Last 45,000 Years,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 5652–7.

22. Mallick 等人，“西蒙斯基因组多样性计划”；M. Lipson 和 D. Reich，“非洲以外现代人类遗传谱系深层关系的工作模型”，分子生物学与进化34 (2017): 889–902。

22. Mallick et al., “Simons Genome Diversity Project”; M. Lipson and D. Reich, “A Working Model of the Deep Relationships of Diverse Modern Human Genetic Lineages Outside of Africa,” Molecular Biology and Evolution 34 (2017): 889–902.

23. Mallick 等人，“西蒙斯基因组多样性计划”；AS Malaspinas 等人，“澳大利亚原住民的基因组历史”，《自然》 538 (2016): 207–14；L. Pagani 等人，“基因组分析揭示了欧亚大陆人口迁徙事件”，《自然》 538 (2016): 238–42。

23. Mallick et al., “Simons Genome Diversity Project”; A. S. Malaspinas et al., “A Genomic History of Aboriginal Australia,” Nature 538 (2016): 207–14; L. Pagani et al., “Genomic Analyses Inform on Migration Events During the Peopling of Eurasia,” Nature 538 (2016): 238–42.

24. Hublin，“现代人类对西欧亚大陆的殖民化”。

24. Hublin, “Modern Human Colonization of Western Eurasia.”

25. M. Raghavan 等人，“西伯利亚旧石器时代晚期基因组揭示了美洲原住民的双重祖先”，《自然》（2013 年）：doi：10.1038/nature12736。

25. M. Raghavan et al., “Upper Palaeolithic Siberian Genome Reveals Dual Ancestry of Native Americans,” Nature (2013): doi: 10.1038/nature12736.

26. Hugo 泛亚洲 SNP 联盟，“绘制亚洲人类遗传多样性图谱”，《科学》 326 (2009): 1541–45。

26. Hugo Pan-Asian SNP Consortium, “Mapping Human Genetic Diversity in Asia,” Science 326 (2009): 1541–45.

27. S. Ramachandran 等人，“人类群体遗传和地理距离关系对起源于非洲的连续奠基者效应的支持”，《美国国家科学院院刊》 102 (2005): 15942–47；BM Henn、LL Cavalli-Sforza 和 MW Feldman，“人类大扩张”，《美国国家科学院院刊》 109 (2012): 17758–64。

27. S. Ramachandran et al., “Support from the Relationship of Genetic and Geographic Distance in Human Populations for a Serial Founder Effect Originating in Africa,” Proceedings of the National Academy of Sciences of the U.S.A. 102 (2005): 15942–47; B. M. Henn, L. L. Cavalli-Sforza, and M. W. Feldman, “The Great Human Expansion,” Proceedings of the National Academy of Sciences of the U.S.A. 109 (2012): 17758–64.

28. JK Pickrell 和 D. Reich，“基于古代 DNA 的人类基因新历史和地理”，遗传学趋势30 (2014): 377–89。

28. J. K. Pickrell and D. Reich, “Toward a New History and Geography of Human Genes Informed by Ancient DNA,” Trends in Genetics 30 (2014): 377–89.

29. 来自大卫·赖希实验室的未发表结果。

29. Unpublished results from David Reich’s laboratory.

30. V. Siska 等人，“来自两个距今 7700 年的早期新石器时代东亚个体的全基因组数据”，《科学进展》 3 (2017): e1601877。

30. V. Siska et al., “Genome-Wide Data from Two Early Neolithic East Asian Individuals Dating to 7700 Years Ago,” Science Advances 3 (2017): e1601877.

31. Peter Bellwood，《第一批农民：农业社会的起源》（马萨诸塞州马尔登：布莱克威尔出版社，2005 年）。

31. Peter Bellwood, First Farmers: The Origins of Agricultural Societies (Malden, MA: Blackwell, 2005).

32. J. Diamond 和 P. Bellwood，“农民及其语言：最初的扩张”，《科学》 300（2003）：597–603。

32. J. Diamond and P. Bellwood, “Farmers and Their Languages: The First Expansions,” Science 300 (2003): 597–603.

33. S. Xu 等人，“汉族人口亚结构的基因组解析及其在关联研究中的意义”，《美国人类遗传学杂志》 85 (2009): 762–74；JM Chen 等人，“全基因组 SNP 变异揭示汉族人口的遗传结构”，《美国人类遗传学杂志》 85 (2009): 775–85。

33. S. Xu et al., “Genomic Dissection of Population Substructure of Han Chinese and Its Implication in Association Studies,” American Journal of Human Genetics 85 (2009): 762–74; J. M. Chen et al., “Genetic Structure of the Han Chinese Population Revealed by Genome-Wide SNP Variation,” American Journal of Human Genetics 85 (2009): 775–85.

34. B. Wen 等人，“遗传证据支持汉文化的流行传播”，《自然》 431（2004）：302-5。

34. B. Wen et al., “Genetic Evidence Supports Demic Diffusion of Han Culture,” Nature 431 (2004): 302–5.

35. FH Chen 等人，“农业促进了人类在公元前 3600 年后在青藏高原的永久居住”，《科学》 347 (2015): 248–50。

35. F. H. Chen et al., “Agriculture Facilitated Permanent Human Occupation of the Tibetan Plateau After 3600 B.P.,” Science 347 (2015): 248–50.

36. 来自大卫·赖希实验室的未发表结果。

36. Unpublished results from David Reich’s laboratory.

37. TA Jinam 等人，“日本北部阿伊努人的独特特征”，《人类遗传学杂志》 60（2015）：565-71。

37. T. A. Jinam et al., “Unique Characteristics of the Ainu Population in Northern Japan,” Journal of Human Genetics 60 (2015): 565–71.

38. 同上；PR Loh 等人，“利用连锁不平衡推断人类群体的混合历史”，遗传学193 (2013): 1233–54。

38. Ibid.; P. R. Loh et al., “Inferring Admixture Histories of Human Populations Using Linkage Disequilibrium,” Genetics 193 (2013): 1233–54.

39. David Reich 实验室未发表的结果；Bellwood，《第一批移民》。

39. Unpublished results from David Reich’s laboratory; Bellwood, First Migrants.

40. Diamond 和 Bellwood，《农民及其语言》。

40. Diamond and Bellwood, “Farmers and Their Languages.”

41. M. Lipson 等人，“重建东南亚岛屿的南岛语族人口历史”，《自然通讯》 5 (2014): 4689。

41. M. Lipson et al., “Reconstructing Austronesian Population History in Island Southeast Asia,” Nature Communications 5 (2014): 4689.

42. R. Blench，“在南岛语族扩张之前，东南亚岛屿地区是否存在南亚语族的存在？”，印度-太平洋史前协会公报30 (2010): 133–44。

42. R. Blench, “Was There an Austroasiatic Presence in Island Southeast Asia Prior to the Austronesian Expansion?,” Bulletin of the Indo-Pacific Prehistory Association 30 (2010): 133–44.

43. 贝尔伍德，《第一批移民》。

43. Bellwood, First Migrants.

44. A. Crowther 等人，“古代作物提供了南岛语族向西扩张的第一个考古学证据”，美国国家科学院院刊113 (2016): 6635–40。

44. A. Crowther et al., “Ancient Crops Provide First Archaeological Signature of the Westward Austronesian Expansion,” Proceedings of the National Academy of Sciences of the U.S.A. 113 (2016): 6635–40.

45. Lipson 等人，“重建南岛语族人口历史”。

45. Lipson et al., “Reconstructing Austronesian Population History.”

46. A. Wollstein 等人，“从全基因组数据推断大洋洲的人口历史”，《当代生物学》 20 (2010): 1983–92；M. Kayser，“大洋洲的人类遗传历史：扩散的近观和远观”，《当代生物学》 20 (2010): R194–201；E. Matisoo-Smith，“古代 DNA 与人类在太平洋的定居：综述”，《人类进化杂志》 79 (2015): 93–104。

46. A. Wollstein et al., “Demographic History of Oceania Inferred from Genome-Wide Data,” Current Biology 20 (2010): 1983–92; M. Kayser, “The Human Genetic History of Oceania: Near and Remote Views of Dispersal,” Current Biology 20 (2010): R194–201; E. Matisoo-Smith, “Ancient DNA and the Human Settlement of the Pacific: A Review,” Journal of Human Evolution 79 (2015): 93–104.

47. D. Reich 等人，“丹尼索瓦人种混合与现代人类首次向东南亚和大洋洲的扩散”，《美国人类遗传学杂志》 89 (2011): 516–28；P. Skoglund 等人，“西南太平洋人口的基因组见解”，《自然》 538 (2016): 510–13。

47. D. Reich et al., “Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania,” American Journal of Human Genetics 89 (2011): 516–28; P. Skoglund et al., “Genomic Insights into the Peopling of the Southwest Pacific,” Nature 538 (2016): 510–13.

48. R. Pinhasi 等人，“从人类岩骨内耳部分获得最佳古代 DNA 产量”，PLoS One 10 (2015): e0129102。

48. R. Pinhasi et al., “Optimal Ancient DNA Yields from the Inner Ear Part of the Human Petrous Bone,” PLoS One 10 (2015): e0129102.

49. Skoglund 等人，“基因组见解”。

49. Skoglund et al., “Genomic Insights.”

50. 同上。

50. Ibid.

51. 来自大卫·赖希实验室和约翰内斯·克劳斯实验室的未发表结果。

51. Unpublished results from David Reich’s laboratory and Johannes Krause’s laboratory.

52. 同上。

52. Ibid.

9. 将非洲重新融入人类故事

9 Rejoining Africa to the Human Story

1. J. Lachance 等人，“来自不同非洲狩猎采集者的高覆盖率全基因组序列的进化历史和适应”，Cell 150 (2012): 457–69。

1. J. Lachance et al., “Evolutionary History and Adaptation from High-Coverage Whole-Genome Sequences of Diverse African Hunter-Gatherers,” Cell 150 (2012): 457–69.

2. V. Plagnol 和 JD Wall，“人类群体中可能的祖先结构”，PLoS Genetics 2 (2006): e105；JD Wall、KE Lohmueller 和 V. Plagnol，“检测多个人类群体中的古代混合并估计人口统计参数”，Molecular Biology and Evolution 26 (2009): 1823–27。

2. V. Plagnol and J. D. Wall, “Possible Ancestral Structure in Human Populations,” PLoS Genetics 2 (2006): e105; J. D. Wall, K. E. Lohmueller, and V. Plagnol, “Detecting Ancient Admixture and Estimating Demographic Parameters in Multiple Human Populations,” Molecular Biology and Evolution 26 (2009): 1823–27.

3. MF Hammer 等人，“非洲古老混合的遗传证据”，美国国家科学院院刊108 (2011): 15123–28。

3. M. F. Hammer et al., “Genetic Evidence for Archaic Admixture in Africa,” Proceedings of the National Academy of Sciences of the U.S.A. 108 (2011): 15123–28.

4. K. Harvati 等人，“来自尼日利亚 Iwo Eleru 的晚期石器时代 Calvaria：形态学和年代学”，PLoS One 6 (2011)：e24024； I. Crevecoeur、A. Brooks、I. Ribot、E. Cornelissen 和 P. Semal，“Ishango（刚果民主共和国）的石器时代晚期人类遗骸：对非洲更新世晚期现代人类多样性的新见解”，《美国体质人类学杂志》 96（2016）：35-57。

4. K. Harvati et al., “The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology,” PLoS One 6 (2011): e24024; I. Crevecoeur, A. Brooks, I. Ribot, E. Cornelissen, and P. Semal, “The Late Stone Age Human Remains from Ishango (Democratic Republic of Congo): New Insights on Late Pleistocene Modern Human Diversity in Africa,” American Journal of Physical Anthropology 96 (2016): 35–57.

5. 来自大卫·赖希实验室的未发表结果。

5. Unpublished results from David Reich’s laboratory.

6. D. Richter 等人，“摩洛哥 Jebel Irhoud 古人类化石的时代和中石器时代的起源”，Nature 546 (2017)：293-96； JG Fleagle、Z. Assefa、FH Brown 和 JJ Shea，“埃塞俄比亚南部基比什地层的古人类学：简介”，人类进化杂志55 (2008)：360-65。

6. D. Richter et al., “The Age of the Hominin Fossils from Jebel Irhoud, Morocco, and the Origins of the Middle Stone Age,” Nature 546 (2017): 293–96; J. G. Fleagle, Z. Assefa, F. H. Brown, and J. J. Shea, “Paleoanthropology of the Kibish Formation, Southern Ethiopia: Introduction,” Journal of Human Evolution 55 (2008): 360–65.

7. H. Li 和 R. Durbin，“从个体全基因组序列推断人类人口历史”，《自然》 475 (2011): 493–96。

7. H. Li and R. Durbin, “Inference of Human Population History from Individual Whole-Genome Sequences,” Nature 475 (2011): 493–96.

8. Li 和 Durbin，“人类人口历史的推断”；K. Prüfer 等人，“来自阿尔泰山脉的尼安德特人的完整基因组序列”，《自然》（2013 年）：doi：10.1038/nature12886。

8. Li and Durbin, “Inference of Human Population History”; K. Prüfer et al., “The Complete Genome Sequence of a Neanderthal from the Altai Mountains,” Nature (2013): doi: 10.1038/nature12886.

9. PH Dirks 等人，“南非新星洞穴中纳莱迪人及其相关沉积物的年代”，eLife 6 (2017): e24231。

9. P. H. Dirks et al., “The Age of Homo Naledi and Associated Sediments in the Rising Star Cave, South Africa,” eLife 6 (2017): e24231.

10. I. Gronau 等人，“从个体基因组序列推断古代人类人口统计”，《自然遗传学》 43 (2011): 1031–34。

10. I. Gronau et al., “Bayesian Inference of Ancient Human Demography from Individual Genome Sequences,” Nature Genetics 43 (2011): 1031–34.

11. P. Skoglund 等人，“重建史前非洲人口结构”，Cell 171 (2017): 5694。

11. P. Skoglund et al., “Reconstructing Prehistoric African Population Structure,” Cell 171 (2017): 5694.

12. S. Mallick 等人，“西蒙斯基因组多样性计划：来自 142 个不同种群的 300 个基因组”，《自然》 538 (2016): 201–6；Gronau 等人，“贝叶斯推断”。

12. S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6; Gronau et al., “Bayesian Inference.”

13. SA Tishkoff 等人，“非洲人和非裔美国人的遗传结构和历史”，《科学》 324（2009）：1035-44。

13. S. A. Tishkoff et al., “The Genetic Structure and History of Africans and African Americans,” Science 324 (2009): 1035–44.

14. CJ Holden，“班图语树反映了农业在撒哈拉以南非洲的传播：最大简约分析”，皇家学会B辑——生物科学269（2002）：793-99；P. de Maret，“班图扩张的考古学”，载于《牛津非洲考古学手册》， Peter Mitchell和Paul J. Lane编辑（牛津：牛津大学出版社，2013），627-44。

14. C. J. Holden, “Bantu Language Trees Reflect the Spread of Farming Across Sub-Saharan Africa: A Maximum-Parsimony Analysis,” Proceedings of the Royal Society B—Biological Sciences 269 (2002): 793–99; P. de Maret, “Archaeologies of the Bantu Expansion,” in The Oxford Handbook of African Archaeology, ed. Peter Mitchell and Paul J. Lane (Oxford: Oxford University Press, 2013), 627–44.

15. K. Bostoen 等人，“全新世中晚期古气候变化与西非中部雨林早期班图人扩张”，《当前》人类学56 (2016): 354–84；K. Manning 等人，“来自马里蒂莱姆西山谷的4,500 年前驯化的珍珠粟 ( Pennisetum glaucum )：对另一种谷物驯化途径的新见解”，考古科学杂志38 (2011): 312–22。

15. K. Bostoen et al., “Middle to Late Holocene Paleoclimatic Change and the Early Bantu Expansion in the Rain Forests of Western Central Africa,” Current Anthropology 56 (2016): 354–84; K. Manning et al., “4,500-Year-Old Domesticated Pearl Millet (Pennisetum glaucum) from the Tilemsi Valley, Mali: New Insights into an Alternative Cereal Domestication Pathway,” Journal of Archaeological Science 38 (2011): 312–22.

16. D. Killick，“从开罗到好望角：冶金术在东非和南非的传播”，《世界史前史杂志》 22（2009）：399-414。

16. D. Killick, “Cairo to Cape: The Spread of Metallurgy Through Eastern and Southern Africa,” Journal of World Prehistory 22 (2009): 399–414.

17. 德·马雷，《班图扩张的考古学》。

17. de Maret, “Archaeologies of the Bantu Expansion.”

18. 霍尔顿，《班图语树》。

18. Holden, “Bantu Language Trees.”

19. Bostoen 等人，“全新世中期至晚期”；Manning 等人，“4500 年前”。

19. Bostoen et al., “Middle to Late Holocene”; Manning et al., “4,500-Year-Old.”

20. DJ Lawson、G. Hellenthal、S. Myers 和 D. Falush，“利用密集单倍型数据推断群体结构”，PLoS Genetics 8 (2012): e1002453；G. Hellenthal 等，“人类混合历史的遗传图谱”，Science 343 (2014): 747–51；C. de Filippo、K. Bostoen、M. Stoneking 和 B. Pakendorf，“结合语言学和遗传学证据检验班图语扩张”，Proceedings of the Royal Society B—Biological Sciences 279 (2012): 3256–63；E. Patin 等，“非洲和北美班图语人群的扩散和遗传适应”，Science 356 (2017): 543–46； GB Busby 等人，“撒哈拉以南非洲的基因混合”，eLife 5（2016）：e15266。

20. D. J. Lawson, G. Hellenthal, S. Myers, and D. Falush, “Inference of Population Structure Using Dense Haplotype Data,” PLoS Genetics 8 (2012): e1002453; G. Hellenthal et al., “A Genetic Atlas of Human Admixture History,” Science 343 (2014): 747–51; C. de Filippo, K. Bostoen, M. Stoneking, and B. Pakendorf, “Bringing Together Linguistic and Genetic Evidence to Test the Bantu Expansion,” Proceedings of the Royal Society B—Biological Sciences 279 (2012): 3256–63; E. Patin et al., “Dispersals and Genetic Adaptation of Bantu-Speaking Populations in Africa and North America,” Science 356 (2017): 543–46; G. B. Busby et al., “Admixture Into and Within Sub-Saharan Africa,” eLife 5(2016): e15266.

21. Tishkoff 等人，“遗传结构和历史”；G. Ayodo 等人，“将自然选择的证据与关联分析相结合，提高了检测疟疾抗性变异的能力”，《美国人类遗传学杂志》 81 (2007): 234–42。

21. Tishkoff et al., “Genetic Structure and History”; G. Ayodo et al., “Combining Evidence of Natural Selection with Association Analysis Increases Power to Detect Malaria-Resistance Variants,” American Journal of Human Genetics 81 (2007): 234–42.

22. C. Ehret，“重建非洲古代亲属关系”，载于《早期人类亲属关系：从性到社会再生产》，Nicholas J. Allen、Hilary Callan、Robin Dunbar 和 Wendy James 编辑（马萨诸塞州马尔登：Blackwell，2008 年），第 200-31 页；C. Ehret、SOY Keita 和 P. Newman，“亚非语系的起源”，《科学》 306（2004 年）：1680-81。

22. C. Ehret, “Reconstructing Ancient Kinship in Africa,” in Early Human Kinship: From Sex to Social Reproduction, ed. Nicholas J. Allen, Hilary Callan, Robin Dunbar, and Wendy James (Malden, MA: Blackwell, 2008), 200–31; C. Ehret, S. O. Y. Keita, and P. Newman, “The Origins of Afroasiatic,” Science 306 (2004): 1680–81.

23. J. Diamond 和 P. Bellwood，“农民及其语言：最初的扩张”，《科学》 300 (2003): 597–603；P. Bellwood，“对 Ehret 等人‘亚非语系的起源’的回应”，《科学》 306 (2004): 1681。

23. J. Diamond and P. Bellwood, “Farmers and Their Languages: The First Expansions,” Science 300 (2003): 597–603; P. Bellwood, “Response to Ehret et al. ‘The Origins of Afroasiatic,’ ” Science 306 (2004): 1681.

24. DQ Fuller 和 E. Hildebrand，“非洲的驯化植物”，载于Peter Mitchell 和 Paul J. Lane 编辑的《牛津非洲考古学手册》（牛津：牛津大学出版社，2013 年），507–26；M. Madella 等人，“7000 年前非洲家养谷物的微生物植物学证据”，PLoS One 9 (2014): e110177。

24. D. Q. Fuller and E. Hildebrand, “Domesticating Plants in Africa,” in The Oxford Handbook of African Archaeology, ed. Peter Mitchell and Paul J. Lane (Oxford: Oxford University Press, 2013), 507–26; M. Madella et al., “Microbotanical Evidence of Domestic Cereals in Africa 7000 Years Ago,” PLoS One 9 (2014): e110177.

25. I. Lazaridis 等人，“从基因组学角度了解古代近东农业的起源”，《自然》 536 (2016): 419–24；Skoglund 等人，“重建史前非洲人口结构”。

25. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24; Skoglund et al., “Reconstructing Prehistoric African Population Structure.”

26. Lazaridis 等人，“基因组见解”；Skoglund 等人，“重建史前非洲人口结构”；VJ Schuenemann 等人，“古埃及木乃伊基因组表明罗马时代之后撒哈拉以南非洲血统的增加”，《自然通讯》 8 (2017): 15694。

26. Lazaridis et al., “Genomic Insights”; Skoglund et al., “Reconstructing Prehistoric African Population Structure”; V. J. Schuenemann et al., “Ancient Egyptian Mummy Genomes Suggest an Increase of Sub-Saharan African Ancestry in Post-Roman Periods,” Nature Communications 8 (2017): 15694.

27. T. Güldemann，“语言学家的观点：科伊-夸迪语使用者是南部非洲最早的粮食生产者”，《南部非洲人文》 20（2008）：93-132。

27. T. Güldemann, “A Linguist’s View: Khoe-Kwadi Speakers as the Earliest Food-Producers of Southern Africa,” Southern African Humanities 20 (2008): 93–132.

28. JK Pickrell 等人，“南部和东部非洲的古代西欧亚血统”，美国国家科学院院刊111 (2014): 2632–37。

28. J. K. Pickrell et al., “Ancient West Eurasian Ancestry in Southern and Eastern Africa,” Proceedings of the National Academy of Sciences of the U.S.A. 111 (2014): 2632–37.

29. 帕加尼等人，“埃塞俄比亚遗传多样性”。

29. Pagani et al., “Ethiopian Genetic Diversity.”

30. Skoglund 等人，“重建史前非洲人口结构”。

30. Skoglund et al., “Reconstructing Prehistoric African Population Structure.”

31. Luigi Luca Cavalli-Sforza 和 Francesco Cavalli-Sforza，《伟大的人类迁徙：多样性和演化的历史》（马萨诸塞州雷丁：Addison-Wesley，1995 年）。

31. Luigi Luca Cavalli-Sforza and Francesco Cavalli-Sforza, The Great Human Diasporas: The History of Diversity and Evolution (Reading, MA: Addison-Wesley, 1995).

32. M. Gallego Llorente 等人，“古代埃塞俄比亚基因组揭示了整个非洲大陆广泛的欧亚混合”，《科学》 350 (2015): 820–22。

32. M. Gallego Llorente et al., “Ancient Ethiopian Genome Reveals Extensive Eurasian Admixture Throughout the African Continent,” Science 350 (2015): 820–22.

33. Donald N. Levine，《大埃塞俄比亚：多民族社会的演变》（芝加哥：芝加哥大学出版社，2000 年）。

33. Donald N. Levine, Greater Ethiopia: The Evolution of a Multiethnic Society (Chicago: University of Chicago Press, 2000).

34. L. Van Dorp 等人，“过去 4500 年内埃塞俄比亚阿里地区铁匠和耕种者共同起源的证据：基于聚类的推断的教训”，PLoS Genetics 11 (2015): e1005397。

34. L. Van Dorp et al., “Evidence for a Common Origin of Blacksmiths and Cultivators in the Ethiopian Ari Within the Last 4500 Years: Lessons for Clustering-Based Inference,” PLoS Genetics 11 (2015): e1005397.

35. D. Reich 等人，“重建印度人口历史”，《自然》 461（2009）：489-94。

35. D. Reich et al., “Reconstructing Indian Population History,” Nature 461 (2009): 489–94.

36. Skoglund 等人，“重建史前非洲人口结构”。

36. Skoglund et al., “Reconstructing Prehistoric African Population Structure.”

37. 同上。

37. Ibid.

38. 同上。

38. Ibid.

39. JK Pickrell 等人，“南部非洲的遗传史前史”，《自然通讯》 3 (2012): 1143；CM Schlebusch 等人，“七个科伊桑人群体的基因组变异揭示了适应和复杂的非洲历史”， 《科学》 338 (2012): 374–79；Mallick 等人，“西蒙斯基因组多样性计划”。

39. J. K. Pickrell et al., “The Genetic Prehistory of Southern Africa,” Nature Communications 3 (2012): 1143; C. M. Schlebusch et al., “Genomic Variation in Seven Khoe-San Groups Reveals Adaptation and Complex African History,” Science 338 (2012): 374–79; Mallick et al., “Simons Genome Diversity Project.”

40. ME Prendergast 等人，“东非桑给巴尔大陆岛屿的形成和动物群落消失的考古学”，PLoS One 11 (2016): e0149565。

40. M. E. Prendergast et al., “Continental Island Formation and the Archaeology of Defaunation on Zanzibar, Eastern Africa,” PLoS One 11 (2016): e0149565.

41. Skoglund 等人，“重建史前非洲人口结构”。

41. Skoglund et al., “Reconstructing Prehistoric African Population Structure.”

42. P. Ralph 和 G. Coop，“平行适应：有利等位基因的一次或多次推进？”，遗传学186 (2010): 647–68。

42. P. Ralph and G. Coop, “Parallel Adaptation: One or Many Waves of Advance of an Advantageous Allele?,” Genetics 186 (2010): 647–68.

43. SA Tishkoff 等人，“非洲和欧洲人类乳糖酶持久性的趋同适应”，《自然遗传学》 39 (2007): 31–40。

43. S. A. Tishkoff et al., “Convergent Adaptation of Human Lactase Persistence in Africa and Europe,” Nature Genetics 39 (2007): 31–40.

44. Ralph 和 Coop，“平行适应”。

44. Ralph and Coop, “Parallel Adaptation.”

10 不平等的基因组学

10 The Genomics of Inequality

1. Peter Wade，《拉丁美洲的种族与民族》（伦敦和纽约：冥王星出版社，2010 年）。

1. Peter Wade, Race and Ethnicity in Latin America (London and New York: Pluto Press, 2010).

2. 跨大西洋奴隶贸易数据库，www.slavevoyages.org/​assessment/​estimates。

2. Trans-Atlantic Slave Trade Database, www.slavevoyages.org/​assessment/​estimates.

3. K. Bryc 等人，“美国各地非裔美国人、拉丁裔美国人和欧裔美国人的遗传祖先”，《美国人类遗传学杂志》 96 (2015): 37–53。

3. K. Bryc et al., “The Genetic Ancestry of African Americans, Latinos, and European Americans Across the United States,” American Journal of Human Genetics 96 (2015): 37–53.

4. 皮尔斯·安东尼，《与时间赛跑》（纽约：霍桑出版社，1973 年）。

4. Piers Anthony, Race Against Time (New York: Hawthorn Books, 1973).

5. 1790 年的第一次联邦人口普查记录显示，弗吉尼亚州有 292,627 名男性奴隶，而男性总人口为 747,610 人；可在www.nationalgeographic.org/​media/​us-census-1790/在线查看。

5. The first federal census in 1790 recorded 292,627 male slaves in Virginia out of a total male population of 747,610; available online at www.nationalgeographic.org/​media/​us-census-1790/.

6. Joshua D. Rothman，《邻里臭名昭著：弗吉尼亚州跨越种族界限的性与家庭，1787-1861》（教堂山：北卡罗来纳大学出版社，2003 年）。

6. Joshua D. Rothman, Notorious in the Neighborhood: Sex and Families Across the Color Line in Virginia, 1787–1861 (Chapel Hill: University of North Carolina Press, 2003).

7. EA Foster 等人，“杰斐逊与奴隶育有最后一个孩子”，《自然》 396 (1998): 27–28。

7. E. A. Foster et al., “Jefferson Fathered Slave’s Last Child,” Nature 396 (1998): 27–28.

8. 关于托马斯·杰弗研究委员会报告的声明儿子和萨莉·海明斯”，2000 年 1 月 26 日，可在以下网址在线获取：https://www.monticello.org/​sites/​default/​files/​inline-pdfs/​jefferson-hemings_report.pdf。

8. “Statement on the TJMF Research Committee Report on Thomas Jefferson and Sally Hemings,” January 26, 2000, available online at https://www.monticello.org/​sites/​default/​files/​inline-pdfs/​jefferson-hemings_report.pdf.

9. M. Hemings，“卑微者的生活，第 1 号”，《派克县（俄亥俄州）共和党人报》， 1873 年 3 月 13 日。

9. M. Hemings, “Life Among the Lowly, No. 1,” Pike County (Ohio) Republican, March 13, 1873.

10. EJ Parra 等人，“居住在南卡罗来纳州的地理定义的非裔美国人的祖先比例和混合动态”，《美国体质人类学杂志》 114 (2001): 18–29。

10. E. J. Parra et al., “Ancestral Proportions and Admixture Dynamics in Geographically Defined African Americans Living in South Carolina,” American Journal of Physical Anthropology 114 (2001): 18–29.

11. 同上。

11. Ibid.

12. Bryc 等人，“遗传祖先”。

12. Bryc et al., “Genetic Ancestry.”

13. JN Fenner，“用于基于遗传学的人口分化研究的人类世代间隔的跨文化估计”，《美国体质人类学杂志》 128（2005）：415-23。

13. J. N. Fenner, “Cross-Cultural Estimation of the Human Generation Interval for Use in Genetics-Based Population Divergence Studies,” American Journal of Physical Anthropology 128 (2005): 415–23.

14. David Morgan，《蒙古人》（马尔登，马萨诸塞州和牛津：布莱克威尔出版社，2007 年）。

14. David Morgan, The Mongols (Malden, MA, and Oxford: Blackwell, 2007).

15. T. Zerjal 等人，“蒙古人的遗传遗产”，《美国人类遗传学杂志》 72 (2003): 717–21。

15. T. Zerjal et al., “The Genetic Legacy of the Mongols,” American Journal of Human Genetics 72 (2003): 717–21.

16. LT Moore 等人，“盖尔爱尔兰霸权的 Y 染色体特征”，《美国人类遗传学杂志》 78 (2006): 334–38。

16. L. T. Moore et al., “A Y-Chromosome Signature of Hegemony in Gaelic Ireland,” American Journal of Human Genetics 78 (2006): 334–38.

17. S. Lippold 等人，“人类父系和母系人口历史：来自高分辨率 Y 染色体和 mtDNA 序列的见解”，《研究遗传学》 5 (2014): 13；M. Karmin 等人，“Y 染色体多样性的近期瓶颈与全球文化变化相吻合”，《基因组研究》 25 (2015): 459–66。

17. S. Lippold et al., “Human Paternal and Maternal Demographic Histories: Insights from High-Resolution Y Chromosome and mtDNA Sequences,” Investigative Genetics 5 (2014): 13; M. Karmin et al., “A Recent Bottleneck of Y Chromosome Diversity Coincides with a Global Change in Culture,” Genome Research 25 (2015): 459–66.

18. 同上。

18. Ibid.

19. A. Sherratt，“耕作与畜牧：第二产品革命的各个方面”，载于《过去的模式：纪念大卫·克拉克的研究》， Ian Hodder、Glynn Isaac 和 Norman Hammond 编辑（剑桥：剑桥大学出版社，1981 年），第 261-306 页。

19. A. Sherratt, “Plough and Pastoralism: Aspects of the Secondary Products Revolution,” in Pattern of the Past: Studies in Honour of David Clarke, ed. Ian Hodder, Glynn Isaac, and Norman Hammond (Cambridge: Cambridge University Press, 1981), 261–306.

20. David W. Anthony，《马、轮子和语言：欧亚草原青铜时代骑手如何塑造现代世界》（新泽西州普林斯顿：普林斯顿大学出版社，2007 年）。

20. David W. Anthony, The Horse, the Wheel, and Language: How Bronze-Age Riders from the Eurasian Steppes Shaped the Modern World (Princeton, NJ: Princeton University Press, 2007).

21. W. Haak 等人，“来自草原的大规模迁徙是欧洲印欧语系的来源”，《自然》 522 (2015): 207–11；ME Allentoft 等人，“青铜时代欧亚大陆的人口基因组学”，《自然》 522 (2015): 167–72。

21. W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11; M. E. Allentoft et al., “Population Genomics of Bronze Age Eurasia,” Nature 522 (2015): 167–72.

22. E. Murphy 和 A. Khokhlov，“伏尔加地区史前人口的生物考古学研究”，载于《俄罗斯草原的青铜时代景观：萨马拉河谷项目》，Monumenta Archaeologica 37， David W. Anthony、Dorcas R. Brown、Aleksandr A. Khokhlov、Pavel V. Kuznetsov 和 Oleg D. Mochalov 编辑（洛杉矶：Cotsen 考古研究所出版社，2016 年），第 149-216 页。

22. E. Murphy and A. Khokhlov, “A Bioarchaeological Study of Prehistoric Populations from the Volga Region,” in A Bronze Age Landscape in the Russian Steppes: The Samara Valley Project, Monumenta Archaeologica 37, ed. David W. Anthony, Dorcas R. Brown, Aleksandr A. Khokhlov, Pavel V. Kuznetsov, and Oleg D. Mochalov (Los Angeles: Cotsen Institute of Archaeology Press, 2016), 149–216.

23. Marija Gimbutas，《东欧史前史，第一部分：俄罗斯和波罗的海地区的中石器时代、新石器时代和铜器时代文化》（哈佛大学美国史前研究学院，第 20 号公告）（马萨诸塞州剑桥：皮博迪博物馆，1956 年）。

23. Marija Gimbutas, The Prehistory of Eastern Europe, Part I: Mesolithic, Neolithic and Copper Age Cultures in Russia and the Baltic Area (American School of Prehistoric Research, Harvard University, Bulletin No. 20) (Cambridge, MA: Peabody Museum, 1956).

24. Haak 等人，“大规模迁移”。

24. Haak et al., “Massive Migration.”

25. RS Wells 等人，“欧亚大陆中心地带：Y 染色体多样性的大陆视角”，美国国家科学院院刊98 (2001): 10244–49。

25. R. S. Wells et al., “The Eurasian Heartland: A Continental Perspective on Y-Chromosome Diversity,” Proceedings of the National Academy of Sciences of the U.S.A. 98 (2001): 10244–49.

26. R. Martiniano 等人，“西伊比利亚考古过渡时期的人口基因组学：利用插补和基于单倍型的方法研究古代亚结构”，PLoS Genetics 13 (2017): e1006852。

26. R. Martiniano et al., “The Population Genomics of Archaeological Transition in West Iberia: Investigation of Ancient Substructure Using Imputation and Haplotype-Based Methods,” PLoS Genetics 13 (2017): e1006852.

27. M. Silva 等人，“印度次大陆的遗传年代学表明存在严重的性别偏向性扩散”，BMC 进化生物学17 (2017): 88。

27. M. Silva et al., “A Genetic Chronology for the Indian Subcontinent Points to Heavily Sex-Biased Dispersals,” BMC Evolutionary Biology 17 (2017): 88.

28. Martiniano 等人，“西伊比利亚”；David Reich 实验室未发表的研究结果。

28. Martiniano et al., “West Iberia”; unpublished results from David Reich’s laboratory.

29. JA Tennessen 等人，“人类外显子组深度测序中罕见编码变异的演化和功能影响”，《科学》 337 (2012): 64–69。

29. J. A. Tennessen et al., “Evolution and Functional Impact of Rare Coding Variation from Deep Sequencing of Human Exomes,” Science 337 (2012): 64–69.

30. A. Keinan、JC Mullikin、N. Patterson 和 D. Reich，“人类走出非洲期间 X 染色体遗传漂变的加速”，《自然遗传学》 41 (2009): 66–70；A. Keinan 和 D. Reich，“性别偏向的人口统计学能否解释非非洲人 X 染色体有效种群规模的减少？”，《分子生物学与进化》 27 (2010): 2312–21。

30. A. Keinan, J. C. Mullikin, N. Patterson, and D. Reich, “Accelerated Genetic Drift on Chromosome X During the Human Dispersal out of Africa,” Nature Genetics 41 (2009): 66–70; A. Keinan and D. Reich, “Can a Sex-Biased Human Demography Account for the Reduced Effective Population Size of Chromosome X in Non-Africans?,” Molecular Biology and Evolution 27 (2010): 2312–21.

31. P. Verdu 等人，“中非俾格米人和非俾格米人的社会文化行为、性别偏向混合和有效人口规模”，分子生物学与进化30 (2013): 918–37。

31. P. Verdu et al., “Sociocultural Behavior, Sex-Biased Admixture, and Effective Population Sizes in Central African Pygmies and Non-Pygmies,” Molecular Biology and Evolution 30 (2013): 918–37.

32. S. Mallick 等人，“西蒙斯基因组多样性计划：来自 142 个不同种群的 300 个基因组”，《自然》 538 (2016)：201-6。

32. S. Mallick et al., “The Simons Genome Diversity Project: 300 Genomes from 142 Diverse Populations,” Nature 538 (2016): 201–6.

33. LG Carvajal-Carmona 等人，“哥伦比亚西北部人口创始人中强烈的美洲印第安人/白人性别偏见和可能的塞法迪犹太人贡献”，《美国人类遗传学杂志》 67 (2000): 1287–95。

33. L. G. Carvajal -Carmona et al., “Strong Amerind/White Sex Bias and a Possible Sephardic Contribution Among the Founders of a Population in Northwest Colombia,” American Journal of Human Genetics 67 (2000): 1287–95.

34. Bedoya 等人，“西班牙裔人群的混合动态：南美洲孤立人群核遗传祖先的转变”，美国国家科学院院刊103 (2006): 7234–39。

34. Bedoya et al., “Admixture Dynamics in Hispanics: A Shift in the Nuclear Genetic Ancestry of a South American Population Isolate,” Proceedings of the National Academy of Sciences of the U.S.A. 103 (2006): 7234–39.

35. P. Moorjani 等人，“印度近期人口混合的遗传证据”，《美国人类遗传学杂志》93 (2013): 422–38。

35. P. Moorjani et al., “Genetic Evidence for Recent Population Mixture in India,” American Journal of Human Genetics 93 (2013): 422–38.

36. M. Bamshad 等人，“印度种姓人口起源的遗传证据”，《基因组研究》 11 (2001): 994–1004；D. Reich 等人，“重建印度人口历史”，《自然》 461 (2009): 489–94。

36. M. Bamshad et al., “Genetic Evidence on the Origins of Indian Caste Populations,” Genome Research 11 (2001): 994–1004; D. Reich et al., “Reconstructing Indian Population History,” Nature 461 (2009): 489–94.

37. Bamshad 等人，“遗传证据”；I. Thanseem 等人，“印度低种姓和部落群体之间的遗传亲缘关系：从 Y 染色体和线粒体 DNA 推断”，BMC Genetics 7 (2006): 42。

37. Bamshad et al., “Genetic Evidence”; I. Thanseem et al., “Genetic Affinities Among the Lower Castes and Tribal Groups of India: Inference from Y Chromosome and Mitochondrial DNA,” BMC Genetics 7 (2006): 42.

38. M. Kayser，“大洋洲人类遗传史：扩散的近观和远观”，《当代生物学》 20（2010）：R194–201；P. Skoglund 等人，“西南太平洋人口的基因组见解”，《自然》 538（2016）：510–13。

38. M. Kayser, “The Human Genetic History of Oceania: Near and Remote Views of Dispersal,” Current Biology 20 (2010): R194–201; P. Skoglund et al., “Genomic Insights into the Peopling of the Southwest Pacific,” Nature 538 (2016): 510–13.

39. FM Jordan、RD Gray、SJ Greenhill 和 R. Mace，“母系居住是南岛语系社会的祖先”，皇家学会会刊 B—生物科学276 (2009): 1957–64。

39. F. M. Jordan, R. D. Gray, S. J. Greenhill, and R. Mace, “Matrilocal Residence Is Ancestral in Austronesian Societies,” Proceedings of the Royal Society B—Biological Sciences 276 (2009): 1957–64.

40. Skoglund 等人，“基因组见解”。

40. Skoglund et al., “Genomic Insights.”

41. I. Lazaridis 和 D. Reich，“未能复制草原移民到中欧的性别偏向的遗传信号”，美国国家科学院院刊114 (2017): E3873–74。

41. I. Lazaridis and D. Reich, “Failure to Replicate a Genetic Signal for Sex Bias in the Steppe Migration into Central Europe,” Proceedings of the National Academy of Sciences of the U.S.A. 114 (2017): E3873–74.

11 种族与身份的基因组学

11 The Genomics of Race and Identity

1. 美国疾病控制与预防中心，“按种族和民族划分的前列腺癌发病率”，https://www.cdc.gov/​cancer/​prostate/​statistics/​race.htm。

1. Centers for Disease Control and Prevention, “Prostate Cancer Rates by Race and Ethnicity,” https://www.cdc.gov/​cancer/​prostate/​statistics/​race.htm.

2. N. Patterson 等人，“疾病高密度混合作图方法”基因”，《美国人类遗传学杂志》 74（2004）：979-1000；MW Smith 等人，“非洲裔美国人疾病基因发现的高密度混合图谱”，《美国人类遗传学杂志》 74（2004）：1001-13。

2. N. Patterson et al., “Methods for High-Density Admixture Mapping of Disease Genes,” American Journal of Human Genetics 74 (2004): 979–1000; M. W. Smith et al., “A High-Density Admixture Map for Disease Gene Discovery in African Americans,” American Journal of Human Genetics 74 (2004): 1001–13.

3. ML Freedman 等人，“混合作图确定 8q24 为非裔美国男性前列腺癌风险位点”，美国国家科学院院刊103 (2006): 14068–73。

3. M. L. Freedman et al., “Admixture Mapping Identifies 8q24 as a Prostate Cancer Risk Locus in African-American Men,” Proceedings of the National Academy of Sciences of the U.S.A. 103 (2006): 14068–73.

4. CA Haiman 等人，“8q24 内的多个区域独立影响前列腺癌的风险”，《自然遗传学》 39 (2007): 638–44。

4. C. A. Haiman et al., “Multiple Regions within 8q24 Independently Affect Risk for Prostate Cancer,” Nature Genetics 39 (2007): 638–44.

5. Freedman 等人，“混合映射识别 8q24”。

5. Freedman et al., “Admixture Mapping Identifies 8q24.”

6. MF Ashley Montagu，《人类最危险的神话：种族谬误》（纽约：哥伦比亚大学出版社，1942 年）。

6. M. F. Ashley Montagu, Man’s Most Dangerous Myth: The Fallacy of Race (New York: Columbia University Press, 1942).

7. RC Lewontin，“人类多样性的分配”，进化生物学6 (1972): 381–98。

7. R. C. Lewontin, “The Apportionment of Human Diversity,” Evolutionary Biology 6 (1972): 381–98.

8. JM Stevens，“政府对 NIH 资助的人口遗传学研究进行监督的可行性”，载于 Barbara A. Koenig、Sandra Soo-Jin Lee 和 Sarah S. Richardson 编辑的《基因组时代重新审视种族》（医学人类学研究）（新泽西州新不伦瑞克：罗格斯大学出版社，2008 年），第 320-41 页；J. Stevens，“种族意义和科学方法：NIH 资助的人类变异报告出版物的政策变化”，《健康政策、政治和法律杂志》28（2003 年）：1033-87。

8. J. M. Stevens, “The Feasibility of Government Oversight for NIH-Funded Population Genetics Research,” in Revisiting Race in a Genomic Age (Studies in Medical Anthropology), ed. Barbara A. Koenig, Sandra Soo-Jin Lee, and Sarah S. Richardson (New Brunswick, NJ: Rutgers University Press, 2008), 320–41; J. Stevens, “Racial Meanings and Scientific Methods: Policy Changes for NIH-Sponsored Publications Reporting Human Variation,” Journal of Health Policy, Politics and Law 28 (2003): 1033–87.

9. NA Rosenberg 等人，“人类群体的遗传结构”，《科学》 298（2002）：2381-85。

9. N. A. Rosenberg et al., “Genetic Structure of Human Populations,” Science 298 (2002): 2381–85.

10. D. Serre 和 S. Pääbo，“大陆内部和大陆之间人类遗传多样性梯度的证据”，《基因组研究》 14 (2004): 1679–85；FB Livingstone，“论人类种族的不存在”，《当代人类学》 3 (1962): 279。

10. D. Serre and S. Pääbo, “Evidence for Gradients of Human Genetic Diversity Within and Among Continents,” Genome Research 14 (2004): 1679–85; F. B. Livingstone, “On the Non-Existence of Human Races,” Current Anthropology 3 (1962): 279.

11. J. Dreyfuss，“更接近我们的非洲起源”，《根》，2011 年 10 月 17 日，www.theroot.com/getting-closer-to-our-african-origins-1790866394。

11. J. Dreyfuss, “Getting Closer to Our African Origins,” The Root, October 17, 2011, www.theroot.com/​getting-closer-to-our-african-origins-1790866394.

12. NA Rosenberg 等人，“渐变群、聚类以及研究设计对人类群体结构推断的影响”，PLoS Genetics 1 (2005): e70。

12. N. A. Rosenberg et al., “Clines, Clusters, and the Effect of Study Design on the Inference of Human Population Structure,” PLoS Genetics 1 (2005): e70.

13. EG Burchard 等人，“种族和民族背景在生物医学研究和临床实践中的重要性”，《新英格兰医学杂志》 348 (2003): 1170–75。

13. E. G. Burchard et al., “The Importance of Race and Ethnic Background in Biomedical Research and Clinical Practice,” New England Journal of Medicine 348 (2003): 1170–75.

14. JF Wilson 等人，“可变药物反应的群体遗传结构”，《自然遗传学》29（2001）：265-69。

14. J. F. Wilson et al., “Population Genetic Structure of Variable Drug Response,” Nature Genetics 29 (2001): 265–69.

15. D. Fullwiley，“种族的生物学建构：‘混合’技术和新的基因医学”，《科学的社会研究》 38（2008）：695-735。

15. D. Fullwiley, “The Biologistical Construction of Race: ‘Admixture’ Technology and the New Genetic Medicine,” Social Studies of Science 38 (2008): 695–735.

16. Lewontin，“人类多样性的分配”；AR Templeton，“人类的生物种族”，生物和生物医学科学史与哲学研究44 (2013): 262–71。

16. Lewontin, “The Apportionment of Human Diversity”; A. R. Templeton, “Biological Races in Humans,” Studies in History and Philosophy of Biological and Biomedical Science 44 (2013): 262–71.

17. 拉齐布·汗 (Razib Khan)， www.razib.com/​wordpress。

17. Razib Khan, www.razib.com/​wordpress.

18. Dienekes 的人类学博客， dienekes.blogspot.com。

18. Dienekes’ Anthropology Blog, dienekes.blogspot.com.

19. Eurogenes博客， http://eurogenes.blogspot.com。

19. Eurogenes Blog, http://eurogenes.blogspot.com.

20. 莱昂·波利亚科夫，《雅利安神话：欧洲种族主义和民族主义思想史》（纽约：基础书籍出版社，1974 年）。

20. Léon Poliakov, The Aryan Myth: A History of Racist and Nationalist Ideas in Europe (New York: Basic Books, 1974).

21. B. Arnold，“过去作为宣传：纳粹德国的极权主义考古学”，《古代》 64（1990）：464-78。

21. B. Arnold, “The Past as Propaganda: Totalitarian Archaeology in Nazi Germany,” Antiquity 64 (1990): 464–78.

22. JK Pritchard、JK Pickrell 和 G. Coop，“人类适应的遗传学”tion: Hard Sweeps, Soft Sweeps, and Polygenic Adaptation,” Current Biology 20 (2010): R208–15; RD Hernandez 等人，“Classic Selective Sweeps Were Rare in Recent Human Evolution,” Science 331 (2011): 920–24。

22. J. K. Pritchard, J. K. Pickrell, and G. Coop, “The Genetics of Human Adaptation: Hard Sweeps, Soft Sweeps, and Polygenic Adaptation,” Current Biology 20 (2010): R208–15; R. D. Hernandez et al., “Classic Selective Sweeps Were Rare in Recent Human Evolution,” Science 331 (2011): 920–24.

23. MC Turchin 等人，“欧洲身高相关 SNP 处站立变异的广泛选择证据”，《自然遗传学》 44 (2012): 1015–19。

23. M. C. Turchin et al., “Evidence of Widespread Selection on Standing Variation in Europe at Height-Associated SNPs,” Nature Genetics 44 (2012): 1015–19.

24. Y. Field 等人，“过去 2000 年人类适应性的检测”，《科学》 354 (2016)：760–64。

24. Y. Field et al., “Detection of Human Adaptation During the Past 2000 Years,” Science 354 (2016): 760–64.

25. A. Okbay 等人，“全基因组关联研究发现了 74 个与教育程度相关的基因位点”，《自然》 533 (2016): 539–42。

25. A. Okbay et al., “Genome-Wide Association Study Identifies 74 Loci Associated with Educational Attainment,” Nature 533 (2016): 539–42.

26. 为了根据Benjamin及其同事2016年的研究数据，计算基因预测教育程度最高的5%人群和最低的5%人群之间预期受教育年限的差异，我进行了以下计算：（1）Benjamin及其同事分析的队列中，受教育年限为14.3 ± 3.7年。我根据该研究估计的效应量（以周为单位）为“每个等位基因0.014至0.048个标准差（相当于2.7至9.0周的受教育时间）”，估算出3.7年的标准差。这些数字换算成188周（= 9.0 / 0.048）至193周（= 2.7 / 0.014）。除以每年52周，得出3.7。（2）Benjamin及其同事还报告了一个受教育年限的基因预测因子，该因子可以解释该性状3.2%的方差。因此，预测值与实际值之间的相关性为√0.032 = 0.18。我们可以用二维正态分布来对此进行数学建模。(3) 预测分布中处于后5%（低于平均值1.64个标准差以上）的人受教育年限超过12年的概率，等于预测分布中处于后5%且受教育年限超过12年的人数比例（该比例可以通过计算二维正态分布中符合这些条件的面积得出）除以0.05。由此得出概率为60%。对预测分布中处于前5%的人的比例进行类似计算，得出概率为84%。(4) 本杰明的研究还表明，如果样本量足够大，就有可能构建一个可靠的遗传预测器，该预测器可以解释20%的方差。如果用 20% 而不是 3.2% 重新计算，预测结果显示，在预测分布的后 5% 的人中，有 37% 的人能够完成 12 年的教育，而前 5% 的人中，有 96% 的人能够完成 12 年的教育。

26. To compute the expected difference in number of years of education between the highest 5 percent and lowest 5 percent of genetically predicted educational attainment based on the numbers in the 2016 study by Benjamin and colleagues, I performed the following computation: (1) The number of years of education in the cohort analyzed by Benjamin and colleagues is quoted as 14.3 ± 3.7. I estimated the standard deviation of 3.7 years from the fact that the study estimates the effect size in weeks to be “0.014 to 0.048 standard deviations per allele (2.7 to 9.0 weeks of schooling).” These numbers translate to 188 ( = 9.0 / 0.048) to 193 ( = 2.7 / 0.014) weeks. Dividing by 52 weeks per year gives 3.7. (2) Benjamin and colleagues also report a genetic predictor of number of years of education that explains 3.2 percent of the variance of the trait. Therefore, the correlation between the predicted value and the actual value is √0.032 = 0.18. We can model this mathematically using a two-dimensional normal distribution. (3) The probability that a person who is in the bottom 5% of the predicted distribution (more than 1.64 standard deviations below the average) has more than 12 years of education is then given by the proportion of people who are in the bottom 5 percent of the predicted distribution and also have more than 12 years of education (which can be calculated by measuring the area of the two-dimensional normal distribution that matches these criteria), divided by 0.05. This gives a probability of 60 percent. A similar calculation for the proportion of people in the top 5 percent of the predicted distribution gives a probability of 84 percent. (4) The Benjamin study also suggests that with enough samples it would be possible to build a reliable genetic predictor that accounts for 20 percent of the variance. Redoing the calculation using 20 percent instead of 3.2 percent leads to a prediction that 37 percent of people in the bottom 5 percent of the predicted distribution would complete twelve years of education compared to 96 percent of the top 5 percent.

27. A. Kong 等人，“与教育程度相关的基因组变异的选择”，美国国家科学院院刊114 (2017): E727–32。

27. A. Kong et al., “Selection Against Variants in the Genome Associated with Educational Attainment,” Proceedings of the National Academy of Sciences of the U.S.A. 114 (2017): E727–32.

28. Kong 等人在《针对变异的选择》一文中估计，在过去一个世纪里，在自然选择的压力下，基因预测的受教育年限减少了约 0.1 个标准差。

28. Kong et al., “Selection Against Variants,” estimate that the genetically predicted number of years of education has decreased by an estimated 0.1 standard deviations over the last century under the pressure of natural selection.

29. G. Davies 等人，“英国生物银行 (N=112 151) 认知功能与教育程度的全基因组关联研究”，《分子精神病学》 21 (2016): 758–67；MT Lo 等人，“人格特质的全基因组分析鉴定出六个基因组位点，并显示与精神疾病的相关性”，《自然遗传学》 49 (2017): 152–56。

29. G. Davies et al., “Genome-Wide Association Study of Cognitive Functions and Educational Attainment in UK Biobank (N=112 151),” Molecular Psychiatry 21 (2016): 758–67; M. T. Lo et al., “Genome-Wide Analyses for Personality Traits Identify Six Genomic Loci and Show Correlations with Psychiatric Disorders,” Nature Genetics 49 (2017): 152–56.

30. S. Sniekers 等人，“78,308 个个体的全基因组关联荟萃分析”uals 鉴定出影响人类智力的新位点和基因”，《自然遗传学》 49 (2017): 1107–12。

30. S. Sniekers et al., “Genome-Wide Association Meta-Analysis of 78,308 Individuals Identifies New Loci and Genes Influencing Human Intelligence,” Nature Genetics 49 (2017): 1107–12.

31. I. Mathieson 等人，“230 位古代欧亚人的全基因组选择模式”，《自然》 528 (2015): 499–503；Field 等人，“人类适应的检测”。

31. I. Mathieson et al., “Genome-wide Patterns of Selection in 230 Ancient Eurasians,” Nature 528 (2015): 499–503; Field et al., “Detection of Human Adaptation.”

32. NA Rosenberg 等人，“人类群体的遗传结构”，《科学》 298（2002）：2381-85。

32. N. A. Rosenberg et al., “Genetic Structure of Human Populations,” Science 298 (2002): 2381–85.

33. S. Ramachandran 等人，“人类群体遗传和地理距离关系对起源于非洲的连续奠基者效应的支持”，《美国国家科学院院刊》 102 (2005): 15942–47；BM Henn、LL Cavalli-Sforza 和 MW Feldman，“人类大扩张”，《美国国家科学院院刊》 109 (2012): 17758–64。

33. S. Ramachandran et al., “Support from the Relationship of Genetic and Geographic Distance in Human Populations for a Serial Founder Effect Originating in Africa,” Proceedings of the National Academy of Sciences of the U.S.A. 102 (2005): 15942–47; B. M. Henn, L. L. Cavalli-Sforza, and M. W. Feldman, “The Great Human Expansion,” Proceedings of the National Academy of Sciences of the U.S.A. 109 (2012): 17758–64.

34. JK Pickrell 和 D. Reich，“基于古代 DNA 的人类基因新历史和地理”，遗传学趋势30 (2014): 377–89。

34. J. K. Pickrell and D. Reich, “Toward a New History and Geography of Human Genes Informed by Ancient DNA,” Trends in Genetics 30 (2014): 377–89.

35. M. Raghavan 等人，“西伯利亚旧石器时代晚期基因组揭示了美洲原住民的双重祖先”，《自然》（2013 年）：doi：10.1038/nature 12736。

35. M. Raghavan et al., “Upper Palaeolithic Siberian Genome Reveals Dual Ancestry of Native Americans,” Nature (2013): doi: 10.1038/nature 12736.

36. I. Lazaridis 等人，“从基因组学角度了解古代近东农业的起源”，《自然》 536 (2016): 419–24。

36. I. Lazaridis et al., “Genomic Insights into the Origin of Farming in the Ancient Near East,” Nature 536 (2016): 419–24.

37. Nicholas Wade，《麻烦的遗产：基因、种族和人类历史》（纽约：企鹅出版社，2014 年）。

37. Nicholas Wade, A Troublesome Inheritance: Genes, Race and Human History (New York: Penguin Press, 2014).

38. G. Coop 等人，“棘手的遗产”（致编辑的信），《纽约时报》， 2014 年 8 月 8 日。

38. G. Coop et al., “A Troublesome Inheritance” (letters to the editor), New York Times, August 8, 2014.

39. G. Cochran、J. Hardy 和 H. Harpending，“阿什肯纳兹犹太人智力的自然史”，《生物社会科学杂志》38 (2006): 659–93。

39. G. Cochran, J. Hardy, and H. Harpending, “Natural History of Ashkenazi Intelligence,” Journal of Biosocial Science 38 (2006): 659–93.

40. PF Palamara、T. Lencz、A. Darvasi 和 I. Pe'er，“血缘同一性的长度分布揭示了精细的人口历史”，《美国人类遗传学杂志》 91 (2012): 809–22；M. Slatkin，“创始人效应的群体遗传学检验及其对阿什肯纳兹犹太人疾病的影响”，《美国人类遗传学杂志》 75 (2004): 282–93。

40. P. F. Palamara, T. Lencz, A. Darvasi, and I. Pe’er, “Length Distributions of Identity by Descent Reveal Fine-Scale Demographic History,” American Journal of Human Genetics 91 (2012): 809–22; M. Slatkin, “A Population-Genetic Test of Founder Effects and Implications for Ashkenazi Jewish Diseases,” American Journal of Human Genetics 75 (2004): 282–93.

41. H. Harpending，“家庭的生物学与文明的未来”（第 38 分钟），保护西方文明，2009 年会议，音频可在www.pres​rving​wester​rnciv.com/​audio/​07%20Prof._Henry_Harpending--The_Biology_of_Families_and_the_Future_of_Civilization.mp3 (2009) 获取。

41. H. Harpending, “The Biology of Families and the Future of Civilization” (minute 38), Preserving Western Civilization, 2009 Conference, audio available at www.prese​rving​weste​rnciv.com/​audio/​07%20Prof._Henry_Harpending--The_Biology_of_Families_and_the_Future_of_Civilization.mp3 (2009).

42. G. Clark，“基因资本主义？马尔萨斯时代、制度和现代偏好的形成”（2007 年），www.econ.ucdavis.edu/​faculty/​gclark/​papers/​Capitalism%20Genes.pdf；Gregory Clark，《告别施舍：世界经济简史》（新泽西州普林斯顿：普林斯顿大学出版社，2007 年）。

42. G. Clark, “Genetically Capitalist? The Malthusian Era, Institutions and the Formation of Modern Preferences” (2007), www.econ.ucdavis.edu/​faculty/​gclark/​papers/​Capitalism%20Genes.pdf; Gregory Clark, A Farewell to Alms: A Brief Economic History of the World (Princeton, NJ: Princeton University Press, 2007).

43. 韦德，《棘手的遗产》。

43. Wade, A Troublesome Inheritance.

44. C. Hunt-Grubbe，“沃森博士的基本 DNA”，《星期日泰晤士报》， 2017 年 10 月 14 日。

44. C. Hunt-Grubbe, “The Elementary DNA of Dr. Watson,” The Sunday Times, October 14, 2017.

45. Coop 等人的来信，《纽约时报》。

45. Coop et al. letters, New York Times.

46. David Epstein，《运动基因：非凡运动表现的科学内幕》（纽约：Current出版社，2013年）。

46. David Epstein, The Sports Gene: Inside the Science of Extraordinary Athletic Performance (New York: Current, 2013).

47. 同上。

47. Ibid.

48. 我按如下方式进行了计算。(1) 某性状的第 99.9999999 个百分位数对应于与均值相差 6.0 个标准差，而第 99.99999 个百分位数对应于 5.2 个标准差。因此，0.8 个标准差的偏移对应于个体数量增加 100 倍。(2) 我假设撒哈拉以南非洲人群中 1.33 倍的遗传变异不仅指基因组中的随机突变，也指调节生物性状的突变。根据 JJ Berg 和 G. Coop 在“多基因适应的群体遗传信号” （PLoS Genetics 10 (2014): e1004412）一文中提出的公式，撒哈拉以南非洲人群的标准差预计会高出 1.15 = √1.33 倍，因此非非洲人群中 6.0 个标准差的阈值对应于撒哈拉以南非洲人群的 5.2 = 6.0 / 1.15 倍，从而导致与第 99.9999999 个百分位数以上相同的预测百倍富集。

48. I performed this computation as follows. (1) The 99.9999999th percentile of a trait corresponds to 6.0 standard deviations from the mean, whereas the 99.99999th percentile corresponds to 5.2 standard deviations. Thus a 0.8-standard-deviation shift corresponds to a hundredfold enrichment of individuals. (2) I assumed that the 1.33-fold higher genetic variation in sub-Saharan Africans applies not just to random mutations in the genome, but also to mutations modulating biological traits. The standard deviation is thus expected to be 1.15 = √1.33-fold higher in sub-Saharan Africans based on a formula in J. J. Berg and G. Coop, “A Population Genetic Signal of Polygenic Adaptation,” PLoS Genetics 10 (2014): e1004412, so the 6.0-standard-deviation cutoff in non-Africans corresponds to 5.2 = 6.0 / 1.15 of that in sub-Saharan Africans, leading to the same predicted hundredfold enrichment above the 99.9999999th percentile.

49. W. Haak 等人，“来自草原的大规模迁徙是欧洲印欧语系的来源”，《自然》 522 (2015): 207–11；ME Allentoft 等人，“青铜时代欧亚大陆的人口基因组学”，《自然》 522 (2015): 167–72。

49. W. Haak et al., “Massive Migration from the Steppe Was a Source for Indo-European Languages in Europe,” Nature 522 (2015): 207–11; M. E. Allentoft et al., “Population Genomics of Bronze Age Eurasia,” Nature 522 (2015): 167–72.

50. D. Reich 等人，“重建印度人口历史”，《自然》 461 (2009): 489–94；Lazaridis 等人，“基因组见解”。

50. D. Reich et al., “Reconstructing Indian Population History,” Nature 461 (2009): 489–94; Lazaridis et al., “Genomic Insights.”

51. Michael F. Robinson，《失落的白人部落：探险家、科学家和改变大陆的理论》（纽约：牛津大学出版社，2016 年）。

51. Michael F. Robinson, The Lost White Tribe: Explorers, Scientists, and the Theory That Changed a Continent (New York: Oxford University Press, 2016).

52. Alex Haley，《根：一个美国家庭的传奇​​》（纽约：Doubleday出版社，1976年）。

52. Alex Haley, Roots: The Saga of an American Family (New York: Doubleday, 1976).

53. “第 4 集：（2010 年）认识你自己”（第 17 分钟），出自亨利·路易斯·盖茨主持的《美国面孔》节目，http://www.pbs.org/​wnet/​facesofamerica/​video/​episode-4-know-thyself/​237/。

53. “Episode 4: (2010) Know Thyself” (minute 17) in Faces of America with Henry Louis Gates Jr., http://www.pbs.org/​wnet/​facesofamerica/​video/​episode-4-know-thyself/​237/.

54. African Ancestry，“常见问题解答”，“关于结果”，问题 3 (2016)，http://www.africanancestry.com/​faq/。

54. African Ancestry, “Frequently Asked Questions,” “About the Results,” question 3 (2016), http://www.africanancestry.com/​faq/.

55. 德雷福斯，“更接近我们的非洲起源”。

55. Dreyfuss, “Getting Closer to Our African Origins.”

56. S. Sailer，“非洲祖先公司追溯 DNA 根源”，合众国际社，2003 年 4 月 28 日，www.upi.com/​inc/​view.php?StoryID=20030428-074922-7714r。

56. S. Sailer, “African Ancestry Inc. Traces DNA Roots,” United Press International, April 28, 2003, www.upi.com/​inc/​view.php?StoryID=20030428-074922-7714r.

57. 来自大卫·赖希实验室的未发表结果。

57. Unpublished results from David Reich’s laboratory.

58. H. Schroeder 等人，“17 世纪加勒比海被奴役非洲人的全基因组祖先”，《美国国家科学院院刊》 112 (2015): 3669–73。

58. H. Schroeder et al., “Genome-Wide Ancestry of 17th-Century Enslaved Africans from the Caribbean,” Proceedings of the National Academy of Sciences of the U.S.A. 112 (2015): 3669–73.

59. RE Green 等人，“尼安德特人基因组草图序列”，《科学》 328 (2010): 710–22。

59. R. E. Green et al., “A Draft Sequence of the Neanderthal Genome,” Science 328 (2010): 710–22.

60. E. Durand，23andMe：“白皮书 23-05：尼安德特人祖先估计器”（2011 年），https://web.stanford.edu/​class/​gene210/​files/​readings/​23andme_Neanderthal_Ancestry.pdf；S. Sankararaman 等人，“现代人类尼安德特人祖先的基因组图谱”，《自然》 507（2014 年）：354–57。

60. E. Durand, 23andMe: “White Paper 23-05: Neanderthal Ancestry Estimator” (2011), https://web.stanford.edu/​class/​gene210/​files/​readings/​23andme_Neanderthal_Ancestry.pdf; S. Sankararaman et al., “The Genomic Landscape of Neanderthal Ancestry in Present-Day Humans,” Nature 507 (2014): 354–57.

61. Sankararaman 等人，“基因组景观”。

61. Sankararaman et al., “Genomic Landscape.”

62. https://customercare.23andme.com/​hc/​en-us/​articles/​212873707-Neanderthal-Report-Basics , #13514.

62. https://customercare.23andme.com/​hc/​en-us/​articles/​212873707-Neanderthal-Report-Basics, #13514.

12 古代DNA的未来

12 The Future of Ancient DNA

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19. K. Yoshida et al., “The Rise and Fall of the Phytophthora infestans Lineage That Triggered the Irish Potato Famine,” eLife 2 (2013): e00731.

20. C. Warinner 等人，“古代人类口腔中的病原体和宿主免疫”，《自然遗传学》 46 (2014): 336–44。

20. C. Warinner et al., “Pathogens and Host Immunity in the Ancient Human Oral Cavity,” Nature Genetics 46 (2014): 336–44.

21. T. Higham 等人，“尼安德特人消失的时间和时空模式”，《自然》 512 (2014): 306–9。

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22. E. Callaway，“古代基因组为美国部落带来‘灵魂洞穴木乃伊’”，《自然》 540（2016）：178-79。

22. E. Callaway, “Ancient Genome Delivers ‘Spirit Cave Mummy’ to US Tribe,” Nature 540 (2016): 178–79.